Stockholders' Equity and Equity Compensation Plans (Tables)

9 Months Ended

Sep. 30, 2012

Stockholders' Equity and Equity Compensation Plans [Abstract]

Summary of unvested restricted common stock activity

Stock-Based Awards. A summary of our unvested restricted common stock activity during the third quarter and nine months ended September 30, 2012 is as follows:

	Quarter Ended September 30, 2012					Nine Months Ended September 30, 2012
	Shares			Weighted- Average Grant Date Fair Value		Shares			Weighted- Average Grant Date Fair Value
Unvested awards, beginning		2,012,463		$	17.50		1,620,394		$	17.87
Awards granted		55,929			19.81		1,052,620			16.58
Awards forfeited/cancelled		—			—		(64,175	)		17.73
Awards vested		(54,023	)		14.08		(594,470	)		16.27
Unvested awards, ending		2,014,369		$	17.66		2,014,369		$	17.66