Investments (Impaired Mortgage Loans) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Impaired Mortgage Loans
Unpaid Principal Balance	$ 270		$ 294
Recorded Investment	264		288
Valuation allowances	65		66
Carrying Value	552		556
Unpaid Principal Balance	356		339
Recorded Investment	353		334
Unpaid Principal Balance	626		633
Average Recorded Investment	620	719
Interest Income	6	4
Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Carrying Value	199		222
Commercial mortgage loans portfolio segment [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	213		214
Recorded Investment	210		210
Valuation allowances	60		58
Carrying Value	448		448
Unpaid Principal Balance	298		299
Recorded Investment	298		296
Unpaid Principal Balance	511		513
Average Recorded Investment	507	536
Interest Income	3	3
Commercial mortgage loans portfolio segment [Member] | Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Carrying Value	150		152
Agricultural [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	57		68
Recorded Investment	54		66
Valuation allowances	5		7
Carrying Value	95		93
Unpaid Principal Balance	47		35
Recorded Investment	46		34
Unpaid Principal Balance	104		103
Average Recorded Investment	100	169
Interest Income	3	1
Agricultural [Member] | Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Carrying Value	49		59
Residential [Member]
Impaired Mortgage Loans
Unpaid Principal Balance	0		12
Recorded Investment	0		12
Valuation allowances	0		1
Carrying Value	9		15
Unpaid Principal Balance	11		5
Recorded Investment	9		4
Unpaid Principal Balance	11		17
Average Recorded Investment	13	14
Interest Income	0	0
Residential [Member] | Loans with a Valuation Allowance [Member]
Impaired Mortgage Loans
Carrying Value	$ 0		$ 11