Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2007
Net deferred tax assets and liabilities [Abstract]
Total deferred tax assets	$ 997,784,000	$ 683,645,000
Total deferred tax liabilities	(44,350,000)	(86,490,000)
Net deferred tax asset before valuation allowance	953,434,000	597,155,000
Valuation allowance	(965,987,000)	(608,761,000)	410,300,000
Net deferred tax liability	(12,553,000)	(11,606,000)
Components of net deferred tax liability [Abstract]
Convertible debentures	(3,470,000)	(15,785,000)
Net operating loss	866,700,000	506,614,000
Loss reserves	55,615,000	60,478,000
Unrealized (appreciation) depreciation in investments	(14,448,000)	(42,009,000)
Mortgage investments	14,602,000	18,944,000
Deferred compensation	13,288,000	17,447,000
Premium deficiency reserves	25,823,000	47,186,000
Loss due to "other than temporary" impairments	1,088,000	11,068,000
Other, net	(5,764,000)	(6,788,000)
Net deferred tax asset before valuation allowance	953,434,000	597,155,000
Valuation allowance	(965,987,000)	(608,761,000)	410,300,000
Net deferred tax liability	(12,553,000)	(11,606,000)
Components of other comprehensive income (loss) that impact changes to valuation allowance	80,100,000	2,300,000	63,500,000
Tax provision (benefit) [Abstract]
Benefit from income taxes	(330,740,000)	(196,835,000)	(145,334,000)
Change in valuation allowance	329,175,000	198,428,000	149,669,000
(Benefit from) provision for income taxes (note 14)	(1,565,000)	1,593,000	4,335,000
Increase (decrease) in deferred tax valuation allowance, included in other comprehensive income, due to change in deferred tax liability related to unrealized gains/losses on investments	28,100,000	0	22,200,000
Net operating loss carryforwards, regular tax basis	2,477,000,000
Net operating loss carryforwards for computing the alternative minimum tax	1,595,000,000
Components of provisions for (benefit from) income taxes [Abstract]
Current	(4,251,000)	598,000	1,618,000
Deferred	90,000	(945,000)	(19,000)
Other	2,596,000	1,940,000	2,736,000
(Benefit from) provision for income taxes	(1,565,000)	1,593,000	4,335,000
Federal income tax received	7,000,000		289,100,000
Reconciliation of effective income tax rate [Abstract]
Federal statutory income tax benefit rate (in hundredths)	(35.00%)	(35.00%)	(35.00%)
Valuation allowance (in hundredths)	35.40%	41.00%	41.60%
Tax exempt municipal bond interest (in hundredths)	(0.80%)	(5.40%)	(10.50%)
Other, net (in hundredths)	0.20%	(0.30%)	5.10%
Effective income tax (benefit) rate (in hundredths)	(0.20%)	0.30%	1.20%
Information regarding income tax examinations [Abstract]
Amount of IRS assessment for unpaid taxes and penalties related to REMIC issue				190,700,000
Amount of payment made related to the IRS assessment on the REMIC issue				65,200,000
Unrecognized tax benefits [Roll Forward]
Balance at beginning of year	110,080,000	109,282,000	91,117,000
Additions based on tax positions related to the current year	0	0	0
Additions for tax positions of prior years	511,000	798,000	18,165,000
Reductions for tax positions of prior years	(4,041,000)	0	0
Settlements	(2,000,000)	0	0
Balance at end of year	104,550,000	110,080,000	109,282,000
Unrecognized tax benefits [Abstract]
Total amount of unrecognized tax benefits that would affect effective tax rate	92,000,000
Unrecognized tax benefits, interest expense	(1,400,000)
Unrecognized tax benefits, accrued interest	$ 25,300,000	$ 26,700,000