Shareholders' Equity Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended					48 Months Ended
	Dec. 12, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2017
Treasury Stock, Value, Acquired, Cost Method		$ 100,000	$ 139,889	$ 7,658			$ 477,500
Stock Repurchase Program, Authorized Amount		100,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 147,500
Treasury Stock, Shares, Acquired							13,800,000
Treasury Stock, Shares		13,796,696	10,718,319				10,718,319
Treasury Stock, Value		$ 477,572	$ 386,322				$ 386,322
Accelerated Share Repurchases, Settlement (Payment) or Receipt		20,000
Accelerated Share Repurchase Agreement [Member]
Treasury Stock, Shares, Acquired	2,910,150
Treasury Stock, Shares			2,883,349	209,618	5,408,819	2,384,760	2,883,349
Treasury Stock Acquired, Average Cost Per Share			$ 48.51	$ 36.53	$ 32.35	$ 31.46
Treasury Stock, Value		$ 80,000	$ 139,900	$ 7,700	$ 175,000	$ 75,000	$ 139,900