Stockholders' Equity - Share Repurchase Program (Details) - Share repurchase program December 2013 - USD ($)	12 Months Ended			37 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2013
Shareholders' Equity
Total purchases authorized under share repurchase program					$ 150,000,000
Shares repurchased	518,576	2,002,444	1,930,841	4,598,661
Average purchase price (in dollars per share)	$ 15.81	$ 17.45	$ 20.57	$ 18.67
Amount of remaining authorization to repurchase common stock	$ 64,100,000			$ 64,100,000