Investments (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Amortized cost
Amortized cost, fixed maturities	$ 9,095
Estimated fair value
Estimated fair value, fixed maturities	9,571	8,688
Indemnity
Amortized cost
Due in one year or less	63
Due after one year through five years	241
Due after five years through ten years	144
Due after ten years	107
Amortized cost, fixed maturities	555	518
Estimated fair value
Due in one year or less	63
Due after one year through five years	241
Due after five years through ten years	148
Due after ten years	112
Estimated fair value, fixed maturities	564	526
Exchange
Amortized cost
Due in one year or less	450
Due after one year through five years	3,240
Due after five years through ten years	3,327
Due after ten years	1,523
Amortized cost, fixed maturities	8,540	7,801
Estimated fair value
Due in one year or less	457
Due after one year through five years	3,409
Due after five years through ten years	3,482
Due after ten years	1,659
Estimated fair value, fixed maturities	$ 9,007	$ 8,162