Financing Receivables (Credit Quality Information Tables) (Details 3) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 3,523	$ 3,492
Less: allowance for loan losses	$ 29	$ 29	$ 31	$ 32
Commercial Real Estate Portfolio Segment [Member]
Mortgage Loans on Real Estate [Line Items]
Percentage of commercial mortgage loans with highest risk rating	0.00%	0.00%
Financing Receivable, Gross	$ 2,737	$ 2,702
Less: allowance for loan losses	21	21
Total loans, net	$ 2,716	$ 2,681
Percentage of gross commercial mortgage loans	100.00%	100.00%
Commercial Real Estate Portfolio Segment [Member] | Apartment Building [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 563	$ 504
Percentage of gross commercial mortgage loans	21.00%	19.00%
Commercial Real Estate Portfolio Segment [Member] | Hotel [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 41	$ 42
Percentage of gross commercial mortgage loans	2.00%	1.00%
Commercial Real Estate Portfolio Segment [Member] | Industrial [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 450	$ 446
Percentage of gross commercial mortgage loans	16.00%	17.00%
Commercial Real Estate Portfolio Segment [Member] | Mixed use [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 50	$ 49
Percentage of gross commercial mortgage loans	2.00%	2.00%
Commercial Real Estate Portfolio Segment [Member] | Office [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 478	$ 489
Percentage of gross commercial mortgage loans	17.00%	18.00%
Commercial Real Estate Portfolio Segment [Member] | Retail [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 940	$ 950
Percentage of gross commercial mortgage loans	34.00%	35.00%
Commercial Real Estate Portfolio Segment [Member] | Other [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 215	$ 222
Percentage of gross commercial mortgage loans	8.00%	8.00%
Commercial Real Estate Portfolio Segment [Member] | East North Central [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 233	$ 198
Percentage of gross commercial mortgage loans	9.00%	7.00%
Commercial Real Estate Portfolio Segment [Member] | East South Central [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 93	$ 88
Percentage of gross commercial mortgage loans	3.00%	3.00%
Commercial Real Estate Portfolio Segment [Member] | Middle Atlantic [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 201	$ 203
Percentage of gross commercial mortgage loans	7.00%	8.00%
Commercial Real Estate Portfolio Segment [Member] | Mountain [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 241	$ 240
Percentage of gross commercial mortgage loans	9.00%	9.00%
Commercial Real Estate Portfolio Segment [Member] | New England [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 88	$ 91
Percentage of gross commercial mortgage loans	3.00%	3.00%
Commercial Real Estate Portfolio Segment [Member] | Pacific [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 767	$ 746
Percentage of gross commercial mortgage loans	28.00%	28.00%
Commercial Real Estate Portfolio Segment [Member] | South Atlantic [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 756	$ 783
Percentage of gross commercial mortgage loans	28.00%	29.00%
Commercial Real Estate Portfolio Segment [Member] | West North Central [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 223	$ 222
Percentage of gross commercial mortgage loans	8.00%	8.00%
Commercial Real Estate Portfolio Segment [Member] | West South Central [Member]
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Gross	$ 135	$ 131
Percentage of gross commercial mortgage loans	5.00%	5.00%