Investments (Amortized Cost and Fair Value of Fixed Maturities by Contractual Maturities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available For Sale Securities Debt Maturities Amortized Cost
Due in one year or less	$ 637,052
Due after one year through five years	4,116,731
Due after five year through ten years	7,415,405
Due after ten years	6,883,989
Asset and mortgage-backed securities	3,320,169
Total	22,373,346	20,270,734
Available For Sale Securities Debt Maturities Fair Value
Due in one year or less	644,928
Due after one year through five years	4,358,370
Due after five year through ten years	7,871,893
Due after ten years	8,136,071
Asset and mortgage-backed securities	3,469,134
Total	$ 24,480,396	$ 21,474,136