Earnings per Share Repurchase of Common Stock (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock Repurchased and Retired During Period, Value			$ 2,920
10b5-1 share repurchase program [Member]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased	50,000,000		50,000,000
Stock Repurchased and Retired During Period, Shares	100,947	0	100,947	0
Stock Repurchased and Retired During Period, Value	$ 2,900	$ 0	$ 2,900	$ 0