Fair Values of Financial and Nonfinancial Instruments (Details) (USD $)	Jun. 30, 2011	Dec. 31, 2010
Fair value measurement for financial instruments
Marketable securities, available-for-sale	$ 359,006,000	$ 437,795,000
Mortgage loans held-for-sale, unpaid principal balance	14,700,000	9,600,000
Mortgage loans held-for-sale, difference between the aggregate fair value and the aggregate unpaid principal balance	247,000	(86,000)
Number of loans 90 days or more past due	2	2
Mortgage loans held-for-sale, aggregate carrying value of loans with payments 90 days or more past due	527,000	468,000
Mortgage loans held-for-sale, aggregate unpaid principal balance of loans with payments 90 days or more past due	624,000	592,000
U.S. Treasury securities \| Recurring Measurement \| Level 1
Fair value measurement for financial instruments
Fair value of assets	3,157,000	15,863,000
Obligations of U.S. and local government agencies \| Recurring Measurement \| Levels 1 and 2
Fair value measurement for financial instruments
Fair value of assets	36,313,000	33,044,000
Corporate debt securities issued under U.S. government/agency-backed programs \| Recurring Measurement \| Level 2
Fair value measurement for financial instruments
Fair value of assets	6,560,000	170,990,000
Corporate debt securities \| Recurring Measurement \| Level 2
Fair value measurement for financial instruments
Fair value of assets	163,571,000	105,102,000
Asset-backed securities \| Recurring Measurement \| Level 2
Fair value measurement for financial instruments
Fair value of assets	23,477,000	7,632,000
Time deposits \| Recurring Measurement \| Level 2
Fair value measurement for financial instruments
Fair value of assets	45,908,000	76,312,000
Short-term pooled investments \| Recurring Measurement \| Levels 1 and 2
Fair value measurement for financial instruments
Fair value of assets	80,020,000	28,852,000
Recurring Measurement \| Level 1 \| Options on futures contracts
Fair value measurement for financial instruments
Fair value of assets	0	81,000
Recurring Measurement \| Level 2 \| Mortgage loans held-for-sale
Fair value measurement for financial instruments
Fair value of assets	14,951,000	9,534,000
Recurring Measurement \| Level 2 \| Forward-delivery contracts
Fair value measurement for financial instruments
Fair value of assets	(326,000)	719,000
Recurring Measurement \| Level 3 \| Mortgage interest rate lock commitments ("IRLCs")
Fair value measurement for financial instruments
Fair value of assets	3,267,000	1,496,000
U.S. Treasury securities
Fair value measurement for financial instruments
Marketable securities, available-for-sale	3,157,000	15,863,000
Obligations of U.S. and local government agencies
Fair value measurement for financial instruments
Marketable securities, available-for-sale	36,313,000	33,044,000
Corporate debt securities issued under U.S. government/agency-backed programs
Fair value measurement for financial instruments
Marketable securities, available-for-sale	6,560,000	170,990,000
Corporate debt securities
Fair value measurement for financial instruments
Marketable securities, available-for-sale	163,571,000	105,102,000
Asset-backed securities
Fair value measurement for financial instruments
Marketable securities, available-for-sale	23,477,000	7,632,000
Time deposits
Fair value measurement for financial instruments
Marketable securities, available-for-sale	45,908,000	76,312,000
Short-term pooled investments
Fair value measurement for financial instruments
Marketable securities, available-for-sale	$ 80,020,000	$ 28,852,000

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

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

- 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 Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References+ Details