Short-Term Investments (Tables)

12 Months Ended

Dec. 31, 2013

Short-Term Investments And Fair Value Measurement [Abstract]

Available-For-Sale Securities Reported at Fair Value

The following tables summarize, 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.

	December 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash	$	483,959	$	—	$	—		$	483,959
Level 1 securities:
Money market funds	126,208		—		—			126,208
Level 2 securities:
Corporate debt securities	316,465		1,245		(654		)	317,056
Government securities	143,812		287		(18		)	144,081
Asset and mortgage-backed securities	93,118		229		(418		)	92,929
Certificate of deposits	23,425		—		—			23,425
Agency securities	17,951		—		(2		)	17,949
Total (1)	$	1,204,938	$	1,761	$	(1,092	)	$	1,205,607

	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 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 $605.0 million that is included in cash and cash equivalents, $595.4 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 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

Estimated Fair Value Of Short-Term Investments By Contractual Maturity

The estimated fair value of short-term investments by contractual maturity as of December 31, 2013 is as follows:

	(in thousands)
Due within one year	$	144,267
Due after one year and through 5 years	408,048
Due after 5 years and through 10 years	1,703
Due after 10 years	41,422
Total short-term investments	$	595,440