Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturities By Contractual Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, amortized cost	$ 482,284
Due after one year through five years, amortized cost	1,820,680
Due after five years through ten years, amortized cost	1,576,656
Due after ten years, amortized cost	3,626,442
Amortized cost, sub-total	7,506,062
Fixed maturities, amortized cost	9,038,158	$ 9,929,137
Due in one year or less, estimated fair value	485,605
Due after one year through five years, estimated fair value	1,857,267
Due after five years through ten years, estimated fair value	1,663,076
Due after ten years, estimated fair value	3,838,664
Estimated fair value, sub-total	7,844,612
Fixed maturities, estimated fair value	9,394,468	$ 10,422,882
Commercial Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	657,670
Estimated fair value	659,538
Residential Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	837,964
Estimated fair value	854,247
Asset-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	36,462
Estimated fair value	$ 36,071