Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturities By Contractual Maturity Date) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, amortized cost	$ 720,305
Due after one year through five years, amortized cost	1,386,900
Due after five years through ten years, amortized cost	1,654,425
Due after ten years, amortized cost	4,019,238
Amortized cost, sub-total	7,780,868
Total fixed maturities, amortized cost	9,590,337	$ 9,038,158
Due in one year or less, estimated fair value	726,444
Due after one year through five years, estimated fair value	1,441,314
Due after five years through ten years, estimated fair value	1,802,966
Due after ten years, estimated fair value	4,517,015
Estimated fair value, sub-total	8,487,739
Total fixed maturities, estimated fair value	10,399,629	$ 9,394,468
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, amortized cost	975,606
Fixed maturities, estimated fair value	1,023,604
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, amortized cost	805,631
Fixed maturities, estimated fair value	859,944
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, amortized cost	28,232
Fixed maturities, estimated fair value	$ 28,342