Short-term Investments Short-term Investments (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	310,813	$	—	$	—		$	310,813
Level 1 securities:
Money market funds	7,017		—		—			7,017
Level 2 securities:
Corporate debt securities	318,573		1,760		(291		)	320,042
Government and agency securities classified as cash equivalents	105,823		—		—			105,823
Government and agency securities classified as short-term investments	114,110		179		—			114,289
Asset and mortgage-backed securities	173,219		469		(198		)	173,490
Total (1)	$	1,029,555	$	2,408	$	(489	)	$	1,031,474

	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 $418.1 million that is included in cash and cash equivalents, $607.8 million included in short-term investments and $5.6 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 March 31, 2013 is as follows:

	(in thousands)
Due within one year	$	70,895
Due after one year and through 5 years	486,043
Due after 5 years and through 10 years	6,633
Due after 10 years	44,250
Total short-term investments	$	607,821