Income Taxes Level 4 Effective Income Tax Rate Reconciliation (Details) - USD ($)	3 Months Ended			12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Income Tax Examination, Description				The federal audit of the years 2012 and 2013 began in March 2015 and is expected to be completed in 2016. Management believes that adequate provision has been made in the financial statements for any potential adjustments that may result from tax examinations and other tax-related matters for all open tax years.
Unrecognized Tax Benefits, Period Increase (Decrease)				$ 36,000,000
Income Tax Examination, Interest Expense				0	$ 0	$ 5,000,000
Interest Payable	$ 0			0	1,000,000
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount				692,000,000	595,000,000	515,000,000
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount				132,000,000	138,000,000	138,000,000
Effective Income Tax Rate Reconciliation, Deduction, Dividends, Amount				156,000,000	114,000,000	139,000,000
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount				(102,000,000)	5,000,000	(2,000,000)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount				3,000,000	2,000,000	10,000,000
Income Tax Expense (Benefit)				305,000,000	350,000,000	246,000,000
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions			$ 48,000,000	48,000,000
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions		$ 12,000,000		12,000,000
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	60,000,000			94,000,000
Unrecognized Tax Benefits	$ 12,000,000			$ 12,000,000	48,000,000	48,000,000
Valuation Allowance of Deferred Tax Assets [Member]
Income Tax Contingency [Line Items]
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount					$ 5,000,000	$ (2,000,000)