Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2016

Fair Value Disclosures [Abstract]

Schedule of assets measured at fair value on a recurring basis

The Company's assets that are measured at fair value on a recurring basis consist of the following:

			Fair Value Measurements at Reporting Date Using
As of June 30, 2016	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Available-for-sale marketable securities:
Unrestricted
Corporate bonds	$	804,303	—		$	804,303
U.S. government and government agency obligations	63,132		—		63,132
Municipal bonds	12,733		—		12,733
Commercial paper	29,635		—		29,635
Certificates of deposit	8,014		—		8,014
Equity securities	17,613		$	17,613	—
	935,430		17,613		917,817
Restricted
Equity securities	53,078		—		53,078
	$	988,508	$	17,613	$	970,895
As of December 31, 2015
Available-for-sale marketable securities:
Unrestricted
Corporate bonds	$	767,683	—		$	767,683
U.S. government and government agency obligations	51,209		—		51,209
Municipal bonds	17,924		—		17,924
Equity securities	31,467		$	31,467	—
	$	868,283	$	31,467	$	836,816