Shareholders' Equity - Dividends and Stock Repurchase Programs (Details) - USD ($)	4 Months Ended	5 Months Ended	12 Months Ended			14 Months Ended
	Dec. 31, 2016	May 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2016	Sep. 30, 2016	Jun. 30, 2015	May 31, 2014
Dividends
Cash dividends declared (in dollars per share)			$ 0.24	$ 0.24	$ 0.15
Stock Repurchase Programs
Authorized common stock repurchase amount							$ 100,000,000.0	$ 100,000,000	$ 65,000,000
Shares repurchased (in shares)	556,000	584,000			227,000	1,406,773
Amount of shares repurchased	$ 22,800,000	$ 30,000,000	$ 41,200,000	$ 70,500,000	$ 10,000,000	$ 58,900,000
Amount available to repurchase shares under stock repurchase program	$ 77,200,000		$ 77,200,000