Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

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, 2015	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	$	531,492	—		$	531,492
U.S. government and government agency obligations	56,634		—		56,634
Municipal bonds	39,856		—		39,856
Equity securities	89,580		$	89,580	—
	$	717,562	$	89,580	$	627,982
As of December 31, 2014
Available-for-sale marketable securities:
Unrestricted
Corporate bonds	$	547,506	—		$	547,506
U.S. government and government agency obligations	28,553		—		28,553
Municipal bonds	37,038		—		37,038
Equity securities	7,379		$	7,379	—
	620,476		7,379		613,097
Restricted
Equity securities	91,439		—		91,439
	$	711,915	$	7,379	$	704,536