Investments (Details 12) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Total mortgage loans	$ 4,472		$ 4,721
Mortgage loans, non-impaired
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	4,393		4,561
Variable rate mortgage loans	65		79
Total mortgage loans	4,458		4,640
Net carrying value of impaired mortgage loans
Impaired mortgage loans with a valuation allowance	14		81
Total impaired mortgage loans	14		81
Valuation allowance on impaired mortgage loans	9	15
Average carrying value and interest income recognized on impaired mortgage loans
Average impaired mortgage loans	48	99
Rollforward of the valuation allowance on impaired mortgage loans
Valuation allowance on impaired mortgage loans, beginning balance	21	42
Net decrease in valuation allowance	(4)	(26)
Charge offs	(8)	(1)
Valuation allowance on impaired mortgage loans, ending balance	9	15
Mortgage loans, non-impaired | Below 1.0
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	179		153
Total mortgage loans	179		153
Mortgage loans, non-impaired | 1.0 - 1.25
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	597		613
Total mortgage loans	597		613
Mortgage loans, non-impaired | 1.26 - 1.50
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	1,184		1,233
Variable rate mortgage loans	2		2
Total mortgage loans	1,186		1,235
Mortgage loans, non-impaired | Above 1.50
Carrying value of non-impaired mortgage loans, summarized by debt service coverage ratio distribution
Fixed rate mortgage loans	2,433		2,562
Variable rate mortgage loans	63		77
Total mortgage loans	$ 2,496		$ 2,639