Marketable Securities, Available-for-sale (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Marketable Securities, Available-for-sale
Gain from marketable securities, net	$ 519	$ 1,302	$ 965	$ 2,610
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	309,967		309,967		348,628
GROSS UNREALIZED GAINS	875		875		269
GROSS UNREALIZED LOSSES	(204)		(204)		(1,881)
ESTIMATED FAIR VALUE	310,638		310,638		347,016
Total debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	263,468		263,468		322,853
GROSS UNREALIZED GAINS	875		875		269
GROSS UNREALIZED LOSSES	(204)		(204)		(1,881)
ESTIMATED FAIR VALUE	264,139		264,139		321,241
U.S. Treasury securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	7,182		7,182		1,557
GROSS UNREALIZED GAINS	0		0		0
GROSS UNREALIZED LOSSES	(7)		(7)		(2)
ESTIMATED FAIR VALUE	7,175		7,175		1,555
Obligations of U.S. and local government agencies
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	140,646		140,646		147,557
GROSS UNREALIZED GAINS	700		700		123
GROSS UNREALIZED LOSSES	(19)		(19)		(860)
ESTIMATED FAIR VALUE	141,327		141,327		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	1,502		1,502		1,453
GROSS UNREALIZED GAINS	1		1		3
GROSS UNREALIZED LOSSES	0		0		0
ESTIMATED FAIR VALUE	1,503		1,503		1,456
Corporate debt securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	76,568		76,568		126,088
GROSS UNREALIZED GAINS	102		102		101
GROSS UNREALIZED LOSSES	(48)		(48)		(523)
ESTIMATED FAIR VALUE	76,622		76,622		125,666
Asset-backed securities
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	37,570		37,570		46,198
GROSS UNREALIZED GAINS	72		72		42
GROSS UNREALIZED LOSSES	(130)		(130)		(496)
ESTIMATED FAIR VALUE	37,512		37,512		45,744
Time deposits
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	45,471		45,471		25,500
GROSS UNREALIZED GAINS	0		0		0
GROSS UNREALIZED LOSSES	0		0		0
ESTIMATED FAIR VALUE	45,471		45,471		25,500
Short-term pooled investments
Schedule of fair values of available-for-sale marketable securities
AMORTIZED COST	1,028		1,028		275
GROSS UNREALIZED GAINS	0		0		0
GROSS UNREALIZED LOSSES	0		0		0
ESTIMATED FAIR VALUE	$ 1,028		$ 1,028		$ 275

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Number 115

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+ 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