Income Taxes (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2007	Dec. 31, 2014
Tax provision (benefit) [Abstract]
Provision for income tax	$ 47,883,000	$ 23,120,000
Change in valuation allowance	(44,498,000)	(22,394,000)
Provision for income taxes	3,385,000	726,000
Change in deferred tax valuation allowance, included in other comprehensive income	6,500,000	13,300,000
Valuation allowance	851,300,000			902,300,000
Net operating loss carryforwards, regular tax basis	2,300,000,000
Net operating loss carryforwards for computing the alternative minimum tax	1,400,000,000
Information regarding income tax examinations [Abstract]
Amount of IRS assessment for unpaid taxes and penalties related to REMIC issue	197,500,000
Estimate of federal interest that may be due	171,900,000
Amount of payment made related to the IRS assessment on the REMIC issue			65,200,000
Estimate of additional state income taxes and interest that may be due	47,700,000
Amount of IRS assessment for unpaid taxes and penalties related to disallowance of carryback of 2009 net operating loss	261,400,000
Total amount of unrecognized tax benefits	106,400,000
Total amount of the unrecognized tax benefits that would affect our effective tax rate	93,800,000
Unrecognized tax benefits, accrued interest	$ 27,100,000			$ 26,900,000