Subsequent Event - Reinsurance of GMDB and GMIB Business (Details) (New Contract [Member], USD $)	0 Months Ended	3 Months Ended
	Feb. 04, 2013	Mar. 31, 2013
Subsequent Event [Line Items]
Subsequent Event, Date	Feb. 04, 2013
Subsequent Event, Description	Effective February 4, 2013, the Company entered into an agreement with Berkshire Hathaway Life Insurance Company of Nebraska (Berkshire) to reinsure the GMDB and GMIB businesses.
Nature, Purpose and Effect of Reinsurance Transactions	Effective February 4, 2013, the Company entered into an agreement with Berkshire Hathaway Life Insurance Company of Nebraska (Berkshire) to reinsure the GMDB and GMIB businesses. Berkshire will reinsure 100% of the Company's future claim payments, net of retrocessional arrangements in place prior to February 4, 2013, for a reinsurance premium of $2.2 billion. The reinsurance agreement is subject to an overall limit of approximately $3.8 billion plus future premiums collected under the contracts being reinsured that will be paid to Berkshire. The Company estimates that these future premium amounts will be from $0.1 to $0.3 billion and, accordingly, expects future claims of approximately $4 billion to be covered by the agreement.
Ceded Reinsurance Agreement, Premium Amount	$ 2,200,000,000
Ceded Reinsurance Agreement, Coverage Limit, Fixed Portion	3,800,000,000
Ceded Reinsurace Agreement, Covered Claims, Expected Amount	4,000,000,000
Payments for Reinsurance	725,000,000,000
Subsequent Event, After-tax impact to shareholders' net income		500,000,000
Minimum [Member]
Subsequent Event [Line Items]
Ceded Reinsurance Agreement, Coverage Limit, Variable Portion	100,000,000
Maximum [Member]
Subsequent Event [Line Items]
Ceded Reinsurance Agreement, Coverage Limit, Variable Portion	$ 300,000,000