Stockholders' Equity - Number and Cost of Employee Stock Plan Repurchases (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Employee stock plan repurchased (in shares)	474	462	1,157
Employee stock plan repurchased	$ 24,755	$ 22,386	$ 44,169