Income Taxes (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2010
Operating Loss Carryforwards [Line Items]
Income Tax Expense (Benefit)	$ 9,853,000	$ 0
Effective Income Tax Rate, Continuing Operations	0.00%
Deferred tax asset, net	288,764,000		292,082,000
Tax preservation rights plan, per investor maximum acquisition percentage of common stock outstanding				4.95%
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Reserved net deferred tax asset			292,100,000
Deferred Tax Assets, Operating Loss and Tax Credit Carryforwards	$ 267,900,000		$ 274,000,000