Income Tax (Tax Effects of Temporary Differences that Give Rise to Significant Portions of the Deferred Income Tax Asset and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals	$ 125,879	$ 116,106
Deferred Tax Assets Reinsurance Transactions	87,688	63,543
Deferred Tax Assets Cash And Invested Assets	775	5,931
Deferred Tax Assets Investment Income	35,192	0
Deferred Tax Assets Deferred Acquisition Costs Capitalized For Tax	143,003	131,714
Deferred Tax Assets, Operating Loss Carryforwards	325,806	524,501
Deferred Tax Assets Deferred Acquisition Costs Capitalized For Financial Reporting	101,223	77,888
Deferred Tax Assets, Gross	819,566	919,683
Deferred Tax Assets, Valuation Allowance	(133,354)	(127,132)
Deferred Tax Assets, Net	686,212	792,551
Deferred Tax Liabilities [Abstract]
Deferred Tax Liabilities, Deferred Expense, Deferred Policy Acquisition Cost	1,013,642	1,011,753
Deferred Tax Liabilities Reinsurance Transactions	1,773,929	1,509,211
Deferred Tax Liabilities Cash And Invested Assets	505,841	336,870
Deferred Tax Liabilities Investment Income	5,635	14,654
Deferred Tax Liabilities, Unrealized Currency Transaction Gains	91,067	81,492
Deferred Tax Liabilities, Prepaid Expenses	0	1,014
Deferred Tax Liabilities	3,390,114	2,954,994
Net deferred income tax liabilities	2,703,902	2,162,443
Balance Sheet Presentation Of Deferred Tax Liabilities [Abstract]
Deferred Tax Assets, Other	66,738	55,885
Deferred income taxes	$ 2,770,640	$ 2,218,328