Income Tax (Provision for Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
Current Federal Tax Expense (Benefit)	$ 131,108	$ 1,020	$ 1,588
Current Foreign Tax Expense (Benefit)	36,830	47,706	92,045
Current Income Tax Expense (Benefit)	167,938	48,726	93,633
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
Deferred Federal Income Tax Expense (Benefit)	159,853	273,928	193,204
Tax Adjustments, Settlements, and Unusual Provisions	(1,033,755)	0	0
Deferred Foreign Income Tax Expense (Benefit)	26,598	19,849	(44,208)
Deferred income taxes	(847,304)	293,777	148,996
Income Tax Expense (Benefit)	$ (679,366)	$ 342,503	$ 242,629