Income Taxes - Operating Loss Carryforwards (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Change in deferred tax asset valuation allowance	$ (90,200,000)	$ (138,900,000)
Operating loss carryforward, losses When utilized impact additional paid in capital	24,600,000
Adjustments to additional paid-in-capital from net operating losses	9,400,000
Operating loss carryforward limitations on use ownership change amount	50.00%
Operating loss carryforward limitations on use ownership change significant stockholder ownership percentage	5.00%
Operating loss carryforward limitations on use ownership change ownership threshold for change in control	4.99%
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Change in deferred tax asset valuation allowance	(84,300,000)	(124,600,000)
Operating loss carryforwards	2,600,000,000
Operating loss carryforwards, expiration date	2022
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Change in deferred tax asset valuation allowance	(5,900,000)	(11,100,000)
Operating loss carryforwards	2,000,000,000
Operating loss carryforwards, expiration date	2013
Net operating loss carryforwards, amount expiring in current year	69,800,000
Operating Loss Carryforwards, Amount Expired	37,200,000
Texas Margins Tax [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets, operating loss carryforwards, tax effect	$ 1,900,000	$ 1,900,000