Summary of Investments (Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Held-To-Maturity, Amortized Cost
Due in one year or less	$ 135
Due after one year through five years	314
Due after five years through 10 years	0
Due after 10 years	0
Amortized Cost	630	656
Held-To-Maturity, Fair Value
Due in one year or less	136
Due after one year through five years	315
Due after five years through 10 years	0
Due after 10 years	0
Fair Value	640	669
Available-For-Sale, Amortized Cost
Due in one year or less	234,849
Due after one year through five years	886,016
Due after five years through 10 years	818,255
Due after 10 years	467,481
Amortized Cost	2,821,143	2,804,514
Available-For-Sale, Fair Value
Due in one year or less	238,774
Due after one year through five years	934,018
Due after five years through 10 years	845,767
Due after 10 years	466,216
Fair Value	3,063,262	2,980,624
Trading, Amortized Cost
Due in one year or less	1,701
Due after one year through five years	7,416
Due after five years through 10 years	1,139
Due after 10 years	5,211
Amortized Cost	15,467	8,049
Trading, Fair Value
Due in one year or less	1,699
Due after one year through five years	8,715
Due after five years through 10 years	1,563
Due after 10 years	6,328
Fair Value	18,305	9,940
Asset-Backed Securities [Member]
Held-To-Maturity, Amortized Cost
Securities not categorized by contractual maturity	0
Held-To-Maturity, Fair Value
Securities not categorized by contractual maturity	0
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	3,023
Amortized Cost	3,023	3,719
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	3,319
Fair Value	3,319	3,995
Mortgage-Backed Securities [Member]
Held-To-Maturity, Amortized Cost
Securities not categorized by contractual maturity	181
Amortized Cost	181	206
Held-To-Maturity, Fair Value
Securities not categorized by contractual maturity	189
Fair Value	189	215
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	19,654
Amortized Cost	19,654	22,034
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	20,188
Fair Value	20,188	22,066
Collateralized Mortgage Obligations [Member]
Held-To-Maturity, Amortized Cost
Securities not categorized by contractual maturity	0
Held-To-Maturity, Fair Value
Securities not categorized by contractual maturity	0
Available-For-Sale, Amortized Cost
Securities not categorized by contractual maturity	320,180
Amortized Cost	320,180	309,975
Available-For-Sale, Fair Value
Securities not categorized by contractual maturity	315,736
Fair Value	315,736	294,763
Fixed Maturities [Member]
Held-To-Maturity, Amortized Cost
Amortized Cost	630	656
Held-To-Maturity, Fair Value
Fair Value	640	669
Available-For-Sale, Amortized Cost
Amortized Cost	2,749,458	2,733,557
Available-For-Sale, Fair Value
Fair Value	2,824,018	2,751,256
Trading, Amortized Cost
Amortized Cost	15,467
Trading, Fair Value
Fair Value	$ 18,305