Segment Information (Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated Net Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	$ 483	$ 387	$ 282
Parent Company [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(77)	(73)	(85)
Annuities [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	238	177	121
Retirement Plan Services [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	51	49	38
Life Insurance [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	295	268	264
Group Protection [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	12	38	39
Other Operations [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(57)	(71)	(177)
Excluded realized gain (loss) [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	(60)	(95)	(14)
Gain (loss) on early extinguishment of debt [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)			(2)
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
Impairment of intangibles [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)			(2)
Benefit ratio unlocking [Member]
Reconciliation of Federal Income Tax Expense (Benefit) from Segments to Consolidated [Abstract]
Total federal income tax expense (benefit)	$ 3	$ 20	$ 14