Investments (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Amortized cost
Total fixed maturities	$ 8,319
Estimated fair value
Estimated fair value, fixed maturities	8,688	8,159
Indemnity
Amortized cost
Due in one year or less	102
Due after one year through five years	241
Due after five years through ten years	92
Due after ten years	83
Total fixed maturities	518
Estimated fair value
Due in one year or less	102
Due after one year through five years	245
Due after five years through ten years	94
Due after ten years	85
Estimated fair value, fixed maturities	526	452
Exchange
Amortized cost
Due in one year or less	369
Due after one year through five years	2,946
Due after five years through ten years	2,884
Due after ten years	1,602
Total fixed maturities	7,801
Estimated fair value
Due in one year or less	374
Due after one year through five years	3,118
Due after five years through ten years	3,022
Due after ten years	1,648
Estimated fair value, fixed maturities	$ 8,162	$ 7,707