Stockholders' Equity - ESPP Activity (Details) - shares	12 Months Ended
	Dec. 31, 2016	Jul. 25, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total 2016 ESPP securities available at December 31, 2016 (shares)	1,246,939		1,483,231	1,747,586	1,720,752
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total ESPP equity securities available at January 1, 2016 (shares)		250,000	0
Plus: Registration of 2016 ESPP (shares)	250,000
Less: 2016 ESPP common stock purchased by eligible employees, net (shares)	(3,961)
Total 2016 ESPP securities available at December 31, 2016 (shares)	246,039