Income Taxes (Narrative) (Detail) (USD $)	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Non-Variable Interest Entities [Line Items]
Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Net deferred tax asset	$ 1,400,000,000	$ 1,400,000,000
Capital losses carryforward period in years	5 years
Taxable income projections, years		15 years
Maximum taxable income projections, years		20 years
Deferred tax assets related to net unrealized losses on investments	18,000,000	18,000,000
Total deferred tax assets		1,400,000,000
Capital loss carryforward				155,000,000
NOL carryforward				943,000,000
Minimum tax credit carryforward				22,000,000
Non Variable Interest Entities [Member]
Non-Variable Interest Entities [Line Items]
Net deferred tax asset	1,396,000,000	1,396,000,000		1,745,000,000
Valuation allowance	194,000,000	194,000,000		236,000,000
Valuation allowance increase	$ 42,000,000