Investments (Fixed Maturity Securities Pledged And Received As Collateral) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 15,801,362	$ 14,010,604
Available-for-sale Securities	16,173,447	14,885,583
Collateral Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	181,380	127,229
Available-for-sale Securities	194,189	134,863
Collateral Received Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities	243,212	117,227
Reported Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	10,106,789	10,197,489
Estimate of Fair Value Measurement [Member]
Schedule of Available-for-sale Securities [Line Items]
Assets Held-in-trust	$ 10,619,581	$ 10,922,947