Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2016

Accounting Policies [Abstract]

Schedule of Investment Securities

Investment securities consisted of the following (in thousands):

	March 31, 2016
	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Estimated Fair Value
	(unaudited)
U.S. Government Agency Securities	$	67,492	$	14	$	(26	)	$	67,480
FDIC Certificates of Deposit (1)		43,800		6		(1	)		43,805
Certificates of Deposit		197,000		—		—			197,000
Commercial Paper		33,128		6		(16	)		33,118
Corporate Notes/Bonds		77,457		35		(67	)		77,425
	$	418,877	$	61	$	(110	)	$	418,828
	December 31, 2015
	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Estimated Fair Value
U.S. Government Agency Securities	$	61,510	$	—	$	(271	)	$	61,239
FDIC Certificates of Deposit (1)		41,343		1		(11	)		41,333
Certificates of Deposit		219,500		—		—			219,500
Commercial Paper		30,122		—		(48	)		30,074
Corporate Notes/Bonds		76,157		—		(262	)		75,895
	$	428,632	$	1	$	(592	)	$	428,041

Schedule of Fair Value Measurements of Cash Equivalents and Available-for-Sale Investment Securities

The fair value measurements of the Company’s cash equivalents and available-for-sale investment securities are identified in the following tables (in thousands):

			Fair Value Measurements at Reporting Date Using
	March 31, 2016		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	18,737	$	18,737	$	—	$	—
U.S. Government Agency Securities		67,480		—		67,480		—
FDIC Certificates of Deposit		43,805		—		43,805		—
Certificates of Deposit		197,000		—		197,000		—
Commercial Paper		33,118		—		33,118		—
Corporate Notes/Bonds		77,425		—		77,425		—
	$	437,565	$	18,737	$	418,828	$	—

			Fair Value Measurements at Reporting Date Using
	December 31, 2015		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
Money market funds	$	31,114	$	31,114	$	—	$	—
U.S. Government Agency Securities		61,239		—		61,239		—
FDIC Certificates of Deposit		41,333		—		41,333		—
Certificates of Deposit		219,500		—		219,500		—
Commercial Paper		30,074		—		30,074		—
Corporate Notes/Bonds		75,895		—		75,895		—
	$	459,155	$	31,114	$	428,041	$	—

Common Stock Equivalents Excluded in Calculation of Diluted Loss Per Share

The following common stock equivalents were excluded in the calculation of diluted loss per share because their effect would be anti-dilutive as applied to the loss from operations for the three months ended March 31, 2016 and 2015:

	Three Months Ended March 31,
	2016		2015
Stock options		1,282,627		1,621,168
RSUs		19,772		—