Shareholders' Equity (Narrative) (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 10, 2017
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 2,100,000
Acquisition of treasury stock (shares)	1,811
Acquisition of treasury stock (value), total	$ 814,777	$ 485,853	$ 88,338
Value of common shares remaining to be repurchased	$ 102,568
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, additional authorized amount				$ 100,000
Share Repurchase Plans [Member]
Equity, Class of Treasury Stock [Line Items]
Acquisition of treasury stock (shares)	1,811	839	154
Acquisition of treasury stock (value), total	$ 813,881	$ 485,841	$ 87,996