Investments (Schedule Of Amortized Cost And Estimated Fair Value Of Fixed Maturities By Contractual Maturity Date) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Due in one year or less, Amortized Cost	$ 296,224
Due after one year through five years, Amortized Cost	1,356,224
Due after five years through ten years, Amortized Cost	1,601,045
Due after ten years, Amortized Cost	1,524,975
Amortized Cost sub-total	4,778,468
Fixed maturities, Amortized Cost	5,125,773	5,172,952
Due in one year or less, Estimated Fair Value	301,089
Due after one year through five years, Estimated Fair Value	1,460,975
Due after five years through ten years, Estimated Fair Value	1,730,807
Due after ten years, Estimated Fair Value	1,645,073
Estimated Fair Value sub-total	5,137,944
Total fixed maturities, Estimated Fair Value	5,507,664	5,538,174
Residential mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Amortized Cost	331,526	366,859
Total fixed maturities, Estimated Fair Value	353,253	389,184
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, Amortized Cost	15,779	16,096
Total fixed maturities, Estimated Fair Value	$ 16,467	$ 16,818