Federal Income Taxes - Components of Net Deferred Tax Asset (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred federal income tax asset:
Losses and loss adjustments expenses	$ 2,832	$ 4,097	$ 5,906
Net operating loss carryforward	2,088,461	5,013	43
Accruals and reserves	18,276
Accrual class action settlement		1,400	1,400
Total deferred federal income tax asset	2,109,569	10,510	7,349
Deferred federal income tax liabilities:
Net unrealized gains on investments	1,946	1,774	2,764
Total deferred federal income tax liabilities	1,946	1,774	2,764
Less: Valuation allowance	2,107,623	8,736	4,585
Net deferred federal income tax asset