Marketable Securities, Available-for-sale (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012 D	Mar. 31, 2011	Dec. 31, 2011
Marketable Securities, Available-for-sale
Minimum original maturity of time deposits and short-term pooled investments, which are not considered cash equivalents (in days)	90
Gain from marketable securities, net	$ 446	$ 1,308
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	290,286		348,628
GROSS UNREALIZED GAINS	712		269
GROSS UNREALIZED LOSSES	(293)		(1,881)
ESTIMATED FAIR VALUE	290,705		347,016
Total debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	259,017		322,853
GROSS UNREALIZED GAINS	712		269
GROSS UNREALIZED LOSSES	(293)		(1,881)
ESTIMATED FAIR VALUE	259,436		321,241
U.S. Treasury securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	7,679		1,557
GROSS UNREALIZED GAINS	0		0
GROSS UNREALIZED LOSSES	(6)		(2)
ESTIMATED FAIR VALUE	7,673		1,555
Obligations of U.S. and local government agencies
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	133,773		147,557
GROSS UNREALIZED GAINS	506		123
GROSS UNREALIZED LOSSES	(36)		(860)
ESTIMATED FAIR VALUE	134,243		146,820
Corporate debt securities issued under U.S. government/agency-backed programs
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	1,953		1,453
GROSS UNREALIZED GAINS	1		3
GROSS UNREALIZED LOSSES	0		0
ESTIMATED FAIR VALUE	1,954		1,456
Corporate debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	77,581		126,088
GROSS UNREALIZED GAINS	139		101
GROSS UNREALIZED LOSSES	(38)		(523)
ESTIMATED FAIR VALUE	77,682		125,666
Asset-backed securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	38,031		46,198
GROSS UNREALIZED GAINS	66		42
GROSS UNREALIZED LOSSES	(213)		(496)
ESTIMATED FAIR VALUE	37,884		45,744
Time deposits
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	25,408		25,500
GROSS UNREALIZED GAINS	0		0
GROSS UNREALIZED LOSSES	0		0
ESTIMATED FAIR VALUE	25,408		25,500
Short-term pooled investments
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	5,861		275
GROSS UNREALIZED GAINS	0		0
GROSS UNREALIZED LOSSES	0		0
ESTIMATED FAIR VALUE	$ 5,861		$ 275

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)

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-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 item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References+ Details

- 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+ Details