Business, Basis of Presentation and Significant Accounting Policies Revenue Recognition (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Revenue from contract with customer excluding assessed tax percentage	13.70%
Revenue from Contract with Customer, Excluding Assessed Tax	$ 72
Capitalized Contract Cost, Net	91
Capitalized Contract Cost, Amortization	5
Capitalized Contract Cost, Impairment Loss	0
Other assets	173			$ 140
Total assets	108,106			107,972
Deferred income taxes	117			187
Total liabilities	104,734			104,391
Retained earnings (deficit)	201			30
Total shareholder's equity	3,372	$ 3,484		3,581	$ 3,377
Total liabilities and shareholder's equity	108,106			107,972
Operating expenses	108	220
Total benefits and expenses	412	501
Income (loss) before income taxes	112	72
Income tax expense (benefit)	25	18
Net income (loss)	87	54
Net cash provided by operating activities	320	$ 133
Recordkeeping & administration
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	28
Distribution & shareholder servicing
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	44
Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Accounts Receivable, Net	$ 26
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 72
Minimum
Disaggregation of Revenue [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
Maximum
Disaggregation of Revenue [Line Items]
Finite-Lived Intangible Asset, Useful Life	15 years
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ 72
Other assets	$ (91)		90
Deferred Income Tax Liabilities, Net			$ 18
Total assets	(91)
Deferred income taxes	(19)
Total liabilities	(19)
Retained earnings (deficit)	(72)
Total shareholder's equity	(72)
Total liabilities and shareholder's equity	(91)
Operating expenses	1
Total benefits and expenses	1
Income (loss) before income taxes	(1)
Income tax expense (benefit)	0
Net income (loss)	(1)
Net cash provided by operating activities	0
Calculated under Revenue Guidance in Effect before Topic 606 | Accounting Standards Update 2014-09 [Member]
Disaggregation of Revenue [Line Items]
Other assets	82
Total assets	108,015
Deferred income taxes	98
Total liabilities	104,715
Retained earnings (deficit)	129
Total shareholder's equity	3,300
Total liabilities and shareholder's equity	108,015
Operating expenses	109
Total benefits and expenses	413
Income (loss) before income taxes	111
Income tax expense (benefit)	25
Net income (loss)	$ 86