Basis of Presentation and Significant Accounting Policies - Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Other Tax Carryforward [Line Items]
Deferred tax assets, operating loss carryforwards	$ 1,008,492,000	$ 973,560,000
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%
Texas Margins Tax [Member]
Other Tax Carryforward [Line Items]
Deferred tax assets, operating loss carryforwards, tax effect	1,900,000	1,900,000
Internal Revenue Service (IRS) [Member]
Other Tax Carryforward [Line Items]
Operating loss carry forward periods	20
Operating loss carryforwards	2,600,000,000
Operating loss carryforwards, expiration date	2022
State and Local Jurisdiction [Member]
Other Tax Carryforward [Line Items]
Operating loss carry forward periods	from five to 20 years
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