Marketable Securities (Tables)

3 Months Ended

Mar. 31, 2016

Investments, Debt and Equity Securities [Abstract]

Available-for-sale Securities

The following tables summarize the Company's investments in marketable securities:

	Amortized		Unrealized					Fair
As of March 31, 2016	Cost Basis		Gains		Losses			Value
Corporate bonds	$	710,989	$	1,920	$	(879	)	$	712,030
U.S. government and government agency obligations	50,383		194		(2		)	50,575
Municipal bonds	16,113		45		(3		)	16,155
Equity securities	17,005		10,057		(5,647		)	21,415
	$	794,490	$	12,216	$	(6,531	)	$	800,175
As of December 31, 2015
Corporate bonds	$	770,092	$	156	$	(2,565	)	$	767,683
U.S. government and government agency obligations	51,402		—		(193		)	51,209
Municipal bonds	17,930		5		(11		)	17,924
Equity securities	17,005		14,461		—			31,466
	$	856,429	$	14,622	$	(2,769	)	$	868,282

Marketable Securities, Based on Contractual Maturity Dates

The fair values of debt security investments by contractual maturity consist of the following:

	March 31, 2016		December 31, 2015
Maturities within one year	$	244,965	$	236,121
Maturities after one year through five years	533,795		600,695
	$	778,760	$	836,816

Fair Value and Unrealized Losses of Marketable Securities

The following table shows the fair value of the Company's marketable securities that have unrealized losses and that are deemed to be only temporarily impaired, aggregated by investment category and length of time that the individual securities have been in a continuous unrealized loss position.

	Less than 12 Months					12 Months or Greater					Total
As of March 31, 2016	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
Corporate bonds	$	132,085	$	(190	)	$	135,211	$	(689	)	$	267,296	$	(879	)
U.S. government and government agency obligations	7,822		(3		)	—		—			7,822		(3		)
Municipal bonds	2,571		(2		)	—		—			2,571		(2		)
Equity securities	9,353		(5,647		)	—		—			9,353		(5,647		)
	$	151,831	$	(5,842	)	$	135,211	$	(689	)	$	287,042	$	(6,531	)
As of December 31, 2015
Corporate bonds	$	668,199	$	(2,473	)	$	23,749	$	(92	)	$	691,948	$	(2,565	)
U.S. government and government agency obligations	51,215		(193		)	—		—			51,215		(193		)
Municipal bonds	11,917		(11		)	—		—			11,917		(11		)
	$	731,331	$	(2,677	)	$	23,749	$	(92	)	$	755,080	$	(2,769	)