Aggregate investment committed in private equity funds.

Name:	adtn_AggregateInvestmentCommittedInPrivateEquityFunds
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Available for sale debt securities maturity period.

+ Details

Name:	adtn_AvailableForSaleDebtSecuritiesMaturityPeriod
Namespace Prefix:	adtn
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Available For Sale Securities Reset Period Of Interest Rate.

+ Details

Name:	adtn_AvailableForSaleSecuritiesResetPeriodOfInterestRate
Namespace Prefix:	adtn
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Available for sales securities, number of securities held.

+ Details

Name:	adtn_AvailableForSalesSecuritiesNumberOfSecuritiesHeld
Namespace Prefix:	adtn
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Available for sales securities, number of shares held.

+ Details

Name:	adtn_AvailableForSalesSecuritiesNumberOfSharesHeld
Namespace Prefix:	adtn
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Available for sales securities Number of shares sold.

+ Details

Name:	adtn_AvailableForSalesSecuritiesNumberOfSharesSold
Namespace Prefix:	adtn
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Commitments towards private equity funds.

+ Details

Name:	adtn_CommitmentsTowardsPrivateEquityFunds
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Estimated fair value of bond.

+ Details

Name:	adtn_EstimatedFairValueOfBond
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Estimated Fair Value Of Other Investments.

+ Details

Name:	adtn_EstimatedFairValueOfOtherInvestments
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of private equity funds commitments expired year two.

+ Details

Name:	adtn_FairValueOfPrivateEquityFundsCommitmentsExpiredYearTwo
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Investments.

+ Details

Name:	adtn_InvestmentsTextualsAbstract
Namespace Prefix:	adtn
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of marketable equity securities subjected to impairment test.

+ Details

Name:	adtn_NumberOfMarketableEquitySecuritiesSubjectedToImpairmentTest
Namespace Prefix:	adtn
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of private equity funds.

+ Details

Name:	adtn_NumberOfPrivateEquityFunds
Namespace Prefix:	adtn
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of shares traded in European stock exchange per day.

+ Details

Name:	adtn_NumberOfSharesTradedInEuropeanStockExchangePerDay
Namespace Prefix:	adtn
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of marketable securities under credit rating categories.

+ Details

Name:	adtn_PercentageOfMarketableSecuritiesUnderCreditRatingCategories
Namespace Prefix:	adtn
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of variable rate demand notes supported by letters of credit from banks.

+ Details

Name:	adtn_PercentageOfVariableRateDemandNotesSupportedByLettersOfCreditFromBanks
Namespace Prefix:	adtn
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of variable rate demand notes supported by standby purchase agreements.

+ Details

Name:	adtn_PercentageOfVariableRateDemandNotesSupportedByStandbyPurchaseAgreements
Namespace Prefix:	adtn
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Receipt of distribution related to private equity funds.

+ Details

Name:	adtn_ReceiptOfDistributionRelatedToPrivateEquityFunds
Namespace Prefix:	adtn
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Schedule of Available for Sale Securities.

+ Details

Name:	adtn_ScheduleOfAvailableForSaleSecuritiesTextualsAbstract
Namespace Prefix:	adtn
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Securities considered for impairment test.

+ Details

Name:	adtn_SecuritiesConsideredForImpairmentTest
Namespace Prefix:	adtn
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15E
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15C
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 14
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 3
-Subparagraph c
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 19
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 86-40
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesEquitySecurities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 21
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27357-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13, 19
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGain
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the gross unrealized losses for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLosses1
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15C
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 15D
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-1/124-1
-Paragraph 16B
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=6956420&loc=d3e25351-111560

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Staff Position (FSP)
-Number FAS115-2/124-2
-Paragraph 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_ImpairmentOfInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Available-for-Sale Securities
-URI http://asc.fasb.org/extlink&oid=6505594

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Trading Securities
-URI http://asc.fasb.org/extlink&oid=6526789

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 12
-Subparagraph a
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 1
-Subparagraph a, f, g

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6956420&loc=d3e24584-111560

+ Details

Name:	us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Other investments not otherwise specified in the taxonomy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f,g))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 12
-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 7
-Section 03
-Paragraph 1
-Subparagraph g

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_OtherInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the sale of equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 15
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26853-111562

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 16
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 18
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesEquity
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 3
-Subparagraph a
-Article 7

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 325
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6485959&loc=d3e22529-158502

+ Details

Name:	us-gaap_RealizedInvestmentGainsLosses
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Investments which are not defined as or included in marketable (debt, equity, or other) securities whose use is restricted in whole or in part, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

+ Details

Name:	us-gaap_RestrictedInvestments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_ScheduleOfInvestmentsLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Investments (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
Investments (Details Textuals) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	$ 460,576,000		$ 460,576,000		$ 368,286,000
Gross unrealized gain on marketable equity securities	29,660,000		29,660,000		38,545,000
Gross unrealized losses on marketable equity securities	579,000		579,000		382,000
Schedule of Investments [Line Items]
Net realized gain on long-term investments	3,372,000	2,464,000	6,139,000	4,656,000
Investments (Textuals) [Abstract]
Proceeds from sale of Marketable equity securities			4,200,000
Realized gain from sale of marketable equity securities			4,100,000
Restricted certificate of deposit held	48,250,000		48,250,000		48,250,000
Estimated fair value of bond	46,000,000		46,000,000
Other investments carried at cost	2,296,000		2,296,000		2,103,000
Number of private equity funds	2		2
Fair value of other investments	10,500,000		10,500,000
Aggregate Investment committed in private equity funds	7,900,000		7,900,000
Commitments towards private equity funds	7,700,000		7,700,000
Receipt of distribution related to the private equity funds	7,900,000		7,900,000
Private equity funds Commitments expired in 2013			200,000
Securities considered for impairment test			any security with a fair value that has declined from its original or adjusted cost basis by 25% or more for six or more consecutive months.
Number of marketable equity securities			3	3
Deferred Compensation Plan Assets [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	6,789,000		6,789,000		4,246,000
Gross unrealized gain on marketable equity securities	351,000		351,000		770,000
Gross unrealized losses on marketable equity securities	0		0		7,000
Corporate bonds [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	200,889,000		200,889,000		127,072,000
Duration of available-for-sale debt securities (in years)	2.2		2.2
Gross unrealized gain on marketable equity securities	971,000		971,000		630,000
Gross unrealized losses on marketable equity securities	362,000		362,000		229,000
Corporate bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities	318,700,000		318,700,000		198,500,000
Corporate bonds [Member] \| AAA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	1.00%		1.00%
Corporate bonds [Member] \| AA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	14.00%		14.00%
Corporate bonds [Member] \| A Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	55.00%		55.00%
Corporate bonds [Member] \| BBB Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	30.00%		30.00%
Municipal fixed-rate bonds [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	117,854,000		117,854,000		71,467,000
Duration of available-for-sale debt securities (in years)	1.3		1.3
Gross unrealized gain on marketable equity securities	597,000		597,000		268,000
Gross unrealized losses on marketable equity securities	5,000		5,000		13,000
Municipal fixed-rate bonds [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities	318,700,000		318,700,000		198,500,000
Municipal fixed-rate bonds [Member] \| AAA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	24.00%		24.00%
Municipal fixed-rate bonds [Member] \| AA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	58.00%		58.00%
Municipal fixed-rate bonds [Member] \| A Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	18.00%		18.00%
Fixed Income Bond Fund [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	751,000		751,000		746,000
Gross unrealized gain on marketable equity securities	225,000		225,000		220,000
Gross unrealized losses on marketable equity securities	0		0		0
Marketable equity securities [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	39,423,000		39,423,000		48,010,000
Gross unrealized gain on marketable equity securities	27,516,000		27,516,000		36,657,000
Gross unrealized losses on marketable equity securities	212,000		212,000		133,000
Impairment of investments			12,000	42,000
Marketable Single Equity Security [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	24,300,000		24,300,000
Available for sales securities, number of shares held	1,300,000		1,300,000
Available for sale securities, number of shares sold			200,000
Number of shares traded in European stock exchange per day			900,000
Gross unrealized gain on marketable equity securities	23,800,000		23,800,000
Other Equity Securities [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available for sales securities, number of securities held	400		400
Gross unrealized gain on marketable equity securities	3,700,000		3,700,000
Gross unrealized losses on marketable equity securities	200,000		200,000
Municipal Variable Rate Demand Notes [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities, carrying value	94,870,000		94,870,000		116,745,000
Available for sale securities, reset period of interest rate			7 days
Gross unrealized gain on marketable equity securities	0		0		0
Gross unrealized losses on marketable equity securities	0		0		0
Percentage of variable rate demand notes supported by letters of credit from banks	24.00%		24.00%
Percentage of variable rate demand notes supported by standby purchase agreements	76.00%		76.00%
Municipal Variable Rate Demand Notes [Member] \| Significant Other Observable Inputs (Level 2) [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Available-for-sale securities	94,900,000		94,900,000		116,700,000
Municipal Variable Rate Demand Notes [Member] \| AAA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	27.00%		27.00%
Municipal Variable Rate Demand Notes [Member] \| AA Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	63.00%		63.00%
Municipal Variable Rate Demand Notes [Member] \| A Rating [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Percentage of marketable securities under credit rating categories	10.00%		10.00%
Other Long-term Investments [Member]
Schedule of available for sale securities (Textuals) [Abstract]
Impairment of investments			0
Private Equity Funds [Member]
Schedule of Investments [Line Items]
Net realized gain on long-term investments			1,400,000
Contribution to private equity funds	$ 8,400,000		$ 8,400,000