Investments (Mortgage Loans and Valuation Allowance by Portfolio Segment) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Dec. 31, 2012
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	$ 275		$ 622
Evaluated collectively for credit losses	57,459		55,467
Total mortgage loans	57,734		56,089
Specific credit losses	26		66
Non-specifically identified credit losses	281		256
Valuation allowances	307	294	322	326	302	347
Mortgage loan, net of valuation allowance	57,427		55,767
Commercial mortgage loans portfolio segment [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	189		506
Evaluated collectively for credit losses	40,351		40,420
Total mortgage loans	40,540		40,926
Specific credit losses	24		58
Non-specifically identified credit losses	203		200
Valuation allowances	227	230	258	259	242	293
Mortgage loan, net of valuation allowance	40,313		40,668
Agricultural [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	62		100
Evaluated collectively for credit losses	11,867		12,291
Total mortgage loans	11,929		12,391
Specific credit losses	2		7
Non-specifically identified credit losses	36		37
Valuation allowances	38	42	44	50	49	52
Mortgage loan, net of valuation allowance	11,891		12,347
Residential [Member]
Mortgage Loans on Real Estate [Line Items]
Evaluated individually for credit losses	24		16
Evaluated collectively for credit losses	5,241		2,756
Total mortgage loans	5,265		2,772
Specific credit losses	0		1
Non-specifically identified credit losses	42		19
Valuation allowances	42	22	20	17	11	2
Mortgage loan, net of valuation allowance	$ 5,223		$ 2,752