Segment Information (Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated Net Income (Loss)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	$ 276	$ 483	$ 387
Parent Company [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(66)	(77)	(73)
Annuities Segment [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	262	238	177
Retirement Plan Services Segment [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	49	51	49
Life Segment [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	159	295	268
Group Protection Segment [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	23	12	38
Other Operations [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(86)	(57)	(71)
Excluded realized gain (loss) pre-tax [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(116)	(60)	(95)
Reserve changes (net of related amortization) on business sold through reinsurance [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	1	1	1
Benefit ratio unlocking [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	$ (16)	$ 3	$ 20