Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current income tax:
Federal	$ 197	$ 137	$ (167)
State	7	3	3
Total current income tax	204	140	(164)
Deferred income tax:
Federal	(38)	51	360
State	(2)	(1)	(1)
Total deferred income tax	(40)	50	359
Total income tax provision	164	190	195
Reconciliation of aggregate income tax provision from that computed by using the U.S. statutory rate
Tax at U.S. statutory rate (as a percent)	35.00%	35.00%	35.00%
Changes in taxes resulting from:
Tax-exempt interest and dividend income (as a percent)	(9.70%)	(12.60%)	(7.80%)
State taxes, net of federal benefit (as a percent)	0.40%	0.10%	0.10%
Low income housing credit (as a percent)	(4.70%)	(1.60%)	(1.60%)
Foreign tax credit, net of addback (as a percent)	(0.50%)	(1.60%)	(1.40%)
Taxes applicable to prior years (as a percent)	(2.50%)		(2.20%)
Other, net (as a percent)	2.10%	(0.50%)
Income tax provision (as a percent)	20.10%	18.80%	22.10%
Increase in effective tax rates due to out-of-period correction of tax deductions for prior periods related to securities lending activities	32
Deferred income tax assets:
Liabilities for future policy benefits	1,295	1,589
Investment related	161
Capital loss and tax credit carryforwards	5	30
State net operating losses	5	4
Gross deferred income tax assets	1,466	1,623
Less: Valuation Allowance	(5)	(4)
Total deferred income tax assets	1,461	1,619
Deferred income tax liabilities:
Deferred acquisition costs	677	639
Net unrealized gains on Available-for-Sale securities	676	501
Investment related		190
Deferred sales inducement costs	142	180
Other	29	49
Gross deferred income tax liabilities	1,524	1,559
Net deferred income tax assets (liabilities)	(63)	60
Reconciliation of the beginning and ending amount of gross unrecognized tax benefits
Balance at the beginning of the period	134	83	(77)
Additions (reductions) based on tax positions related to the current year	1	(1)
Additions for tax positions of prior years	19	79	322
Reductions for tax positions of prior years	(77)	(7)	(196)
Settlements	(12)	(20)	34
Balance at the end of the period	65	134	83
Unrecognized tax benefits, net of federal tax benefits that would affect the effective tax rate if recognized	8	12	39
Increase (decrease) in interest and penalties	(3)	57	(8)
Payable related to accrued interest and penalties	30	33
Estimated decrease in amount of unrecognized tax benefits in next 12 months	63
Income tax provision (benefit) amounts of items comprising other comprehensive income (loss)
Net unrealized securities gains	161	89	181
Net unrealized derivative losses	(2)	(2)	(2)
Net income tax provision	$ 159	$ 87	$ 179