Stockholders' Equity (Details 2) (Share repurchase program December 2013, USD $)	1 Months Ended	3 Months Ended		16 Months Ended
	Apr. 27, 2015	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2013
Share repurchase program December 2013
Shareholders' Equity
Total purchases authorized under share repurchase program					$ 150,000,000
Shares repurchased	150,700	80,500	1,013,341	2,158,141
Average purchase price (in dollars per share)	$ 21.80	$ 20.88	$ 20.50	$ 20.57
Amount of remaining authorization to repurchase common stock	$ 102,300,000