Stockholders' Equity and Equity Compensation Plans (Tables)

9 Months Ended

Sep. 30, 2017

Stockholders Equity Note [Abstract]

Summary of Unvested Restricted Common Stock Activity

Stock-Based Awards. A summary of our unvested restricted common stock activity during the quarter and nine months ended September 30, 2017 is as follows (shares in thousands):

	Quarter Ended					Nine Months Ended
	September 30, 2017					September 30, 2017
	Shares			Weighted- Average Grant Date Fair Value		Shares			Weighted- Average Grant Date Fair Value
Unvested awards, beginning		1,391		$	34.92		1,394		$	31.26
Awards granted		67			37.96		542			39.30
Awards forfeited/cancelled		(16	)		32.29		(36	)		32.99
Awards vested		(231	)		28.51		(689	)		28.58
Unvested awards, ending		1,211		$	36.34		1,211		$	36.34