Short-term Investments Short-term Investments (Tables)

6 Months Ended

Jun. 30, 2013

Short-Term Investments And Fair Value Measurement [Abstract]

Available-For-Sale Securities Reported At Fair Value

The following table summarizes, by major security type, the Company’s assets that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy:

	As of June 30, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	368,527	$	—	$	—		$	368,527
Level 1 securities:
Money market funds	7,354		—		—			7,354
Level 2 securities:
Corporate debt securities	332,174		918		(1,714		)	331,378
Government and agency securities	181,638		180		(156		)	181,662
Asset and mortgage-backed securities	196,913		276		(797		)	196,392
Total (1)	$	1,086,606	$	1,374	$	(2,667	)	$	1,085,313

	As of December 31, 2012
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	284,661	$	—	$	—		$	284,661
Level 1 securities:
Money market funds	10,500		—		—			10,500
Level 2 securities:
Corporate debt securities	150,322		1,605		(32		)	151,895
Government and agency securities	166,643		285		—			166,928
Asset and mortgage-backed securities	138,340		750		(125		)	138,965
Total (2)	$	750,466	$	2,640	$	(157	)	$	752,949

(1) Includes $370.7 million that is included in cash and cash equivalents, $709.4 million included in short-term investments and $5.2 million of restricted cash that is included in other non-current assets related to workers compensation deposits.

(2) Includes $290.3 million that is included in cash and cash equivalents, $457.8 million included in short-term investments and $4.8 million of restricted cash that is included in other non-current assets related to workers compensation deposits.

Estimated Fair Value Of Short-Term Investments By Contractual Maturity

The estimated fair value of short-term investments by contractual maturity as of June 30, 2013 is as follows:

	(in thousands)
Due within one year	$	138,342
Due after one year and through 5 years	524,210
Due after 5 years and through 10 years	1,755
Due after 10 years	45,125
Total short-term investments	$	709,432