Stockholders' Equity (Details) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 31, 2015	Jun. 30, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 29, 2015	Jun. 05, 2012
Class of Stock [Line Items]
Preferred stock, authorized (in shares)			5,000,000	5,000,000
Preferred stock, issued (in shares)			0	0
Employee stock purchase (in shares)			1,312,812	2,989,324	864,457
Employee stock purchases			$ 33,776,000	$ 65,238,000	$ 17,343,000
Issuance of restricted stock awards (in shares)			132,344	166,042	212,136
Common stock, authorized (in shares)			187,500,000	187,500,000	125,000,000	187,500,000
Issuance of common stock				$ 29,964,000
Stock repurchase program, authorized amount							$ 50,000,000
Repurchase of common stock (in shares)		2,192,982
Repurchase of common stock		$ 50,000,000
Common stock held in treasury (in shares)			2,192,982	2,192,982
Common Stock [Member]
Class of Stock [Line Items]
Employee stock purchase (in shares)			1,313,000	2,989,000	864,000
Employee stock purchases			$ 1,000	$ 3,000	$ 1,000
Issuance of restricted stock awards (in shares)			132,000	166,000	214,000
Issuance of common stock (in shares)	944,537			945,000
Issuance of common stock	$ 30,000,000			$ 1,000