Equity (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity [Abstract]
Stock Repurchase Program, Authorized Amount	$ 400,000	$ 400,000	$ 450,000
Treasury Stock, Shares, Acquired	208,680	1,356,892	4,145,440
Treasury Stock Value Acquired Cost Method Repurchase Agreement	$ 26,900	$ 116,500	$ 375,300
Treasury Stock, Value, Acquired, Cost Method	$ 43,508	$ 122,916	$ 384,519