Net Income Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Mar. 04, 2016
Stock Repurchase Program, Authorized Amount					$ 500,000
Treasury Stock, Shares, Acquired			811,385
Treasury Stock Acquired, Average Cost Per Share			$ 59.44
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 451,773		$ 451,773
Performance Shares [Member]
Antidilutive securities excluded from EPS	137,000	125,000	137,000	125,000