Stockholders' Equity - Share Repurchases (Details) - Share repurchase program December 2013 - USD ($) $ / shares in Units, $ in Millions	9 Months Ended		34 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2013
Shareholders' Equity
Total purchases authorized under share repurchase program				$ 150.0
Shares repurchased	518,576	1,263,791	4,598,661
Average purchase price (in dollars per share)	$ 15.81	$ 18.04	$ 18.67
Amount of remaining authorization to repurchase common stock	$ 64.1		$ 64.1