Income Tax (Total Income Taxes Provided) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Effects Allocated Directly to Equity [Abstract]
Income Tax Expense (Benefit)	$ (679,366)	$ 342,503	$ 242,629
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax	306,849	157,929	(339,889)
Income Tax Effects Allocated Directly to Equity, Employee Stock Options	0	(162)	(2,963)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(42,153)	21,081	16,478
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	404	1,772	1,726
Income Tax Expense (Benefit), Intraperiod Tax Allocation	$ (414,266)	$ 523,123	$ (82,019)