Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 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 March 31, 2016	Fair Value		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Available-for-sale marketable securities:
Corporate bonds	$	712,030	—		$	712,030
U.S. government and government agency obligations	50,575		—		50,575
Municipal bonds	16,155		—		16,155
Equity securities	21,415		$	21,415	—
	$	800,175	$	21,415	$	778,760
As of December 31, 2015
Available-for-sale marketable securities:
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	31,466		$	31,466	—
	$	868,282	$	31,466	$	836,816