Stockholders' Equity and Equity Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2018

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 ended March 31, 2018 is as follows (shares in thousands):

	Quarter Ended
	March 31, 2018
	Shares			Weighted- Average Grant Date Fair Value
Unvested awards, beginning		1,222		$	36.84
Awards granted		450			47.01
Awards forfeited/cancelled		(59	)		39.72
Awards vested		(397	)		33.76
Unvested awards, ending		1,216		$	41.48