Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Available for Sale Amortized Cost
Due in one year or less	$ 432,502
Due after one year through five years	864,299
Due after five years through ten years	642,273
Due after ten years	419,497
Total	3,079,002	3,827,496
Available for Sale Securities Fair Value
Due in one year or less	438,120
Due after one year through five years	936,644
Due after five years through ten years	696,655
Due after ten years	457,327
Total	3,264,216	4,203,450
Residential Mortgage Backed Securities [Member]
Available for Sale Amortized Cost
Debt Maturities, without single maturity date	152,779
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date	156,945
Commercial Mortgage Backed Securities [Member]
Available for Sale Amortized Cost
Debt Maturities, without single maturity date	384,764
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date	390,633
Asset-backed Securities [Member]
Available for Sale Amortized Cost
Debt Maturities, without single maturity date	182,888
Available for Sale Securities Fair Value
Debt Maturities, without Single Maturity Date	$ 187,892