Fair Value of Assets and Liabilities (Level 3 Assets and Liabilities)(Footnotes to Table) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair value, assets and liabilities gain (loss) included in earnings	$ 8	$ (16)
Total gains (losses) included in: Net income	5	(1)
Other investments: Free-standing derivatives	1	1
Free-standing derivatives, liabilities	2	9
Realized capital gains and losses
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) included in: Net income	1	(4)
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	1	(18)
Net investment income
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) included in: Net income	5	3
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	5	3
Interest credited to contractholder funds
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total gains (losses) included in: Net income	(5)	1
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	(5)	1
Contract benefits
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Gains (losses) for Level 3 assets and liabilities still held at the balance sheet date	$ 7	$ (16)