Income Taxes (Reconciliation of Income Tax Provision) (Details 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of the income tax provision
Tax at U.S. statutory rate (as a percent)	35.00%	35.00%	35.00%
Changes in taxes resulting from:
Impact of the Tax Act (as a percent)	13.00%
Dividend received deduction (as a percent)	(5.80%)	(7.60%)	(6.70%)
Low income housing tax credit (as a percent)	(3.40%)	(4.20%)	(3.00%)
Incentive compensation (as a percent)	(3.00%)
Foreign taxes (as a percent)	(2.00%)	(2.50%)	0.00%
Foreign tax credits, net of addback (as a percent)	(0.00%)	(1.60%)	(2.10%)
Taxes applicable to prior years (as a percent)	0.00%	(3.10%)	0.00%
State taxes, net of federal benefit (as a percent)	0.00%	1.90%	0.00%
Net income (loss) attributable to noncontrolling interests (as a percent)	0.00%	0.00%	(2.00%)
Other, net (as a percent)	(0.70%)	(0.50%)	0.10%
Income tax provision (as a percent)	33.10%	17.40%	21.30%
Expense related to the enactment of the Tax Act	$ 286
Net excess tax benefit recognized in income tax provisions	70
Benefits Tax Planning and Completion of Audits		$ 27
Income taxes expense from continuing operations related to Tax Act	278
Tax Act provisional tax to remeasure deferred tax assets and liabilities	221
Provisional tax related to the foreign provisions of the Tax Act	57
Accumulated Earnings of Foreign Subsidiaries	$ 429