Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2017

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 September 30, 2017	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	$	1,564,489	—		$	1,564,489
U.S. government and government agency obligations	189,058		—		189,058
Municipal bonds	4,606		—		4,606
Commercial paper	61,464		—		61,464
Certificates of deposit	6,525		—		6,525
Equity securities	88,040		$	88,040	—
	$	1,914,182	$	88,040	$	1,826,142
As of December 31, 2016
Available-for-sale marketable securities:
Corporate bonds	$	1,072,851	—		$	1,072,851
U.S. government and government agency obligations	132,340		—		132,340
Municipal bonds	7,644		—		7,644
Commercial paper	63,075		—		63,075
Certificates of deposit	42,612		—		42,612
Equity securities	49,219		$	49,219	—
	$	1,367,741	$	49,219	$	1,318,522