Income Taxes (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013 item	Jun. 30, 2012	Jun. 30, 2013 item	Jun. 30, 2012	Dec. 31, 2012
Income Taxes
Number of consecutive quarters of earnings considered for valuation allowance	5		5
Reversal of deferred tax asset valuation allowance	$ (187,500,000)
Valuation allowance against deferred tax assets	46,400,000		46,400,000		258,900,000
Overall effective income tax (benefit) expense rate (as a percent)	(422.60%)	2.90%	(280.60%)	14.00%
Tax (benefit) expense	(186,952,000)	190,000	(186,753,000)	190,000
Federal
Income Taxes
Period of net operating losses carryforward			20 years
Period of federal tax credit carryforwards			5 years
State
Income Taxes
Tax (benefit) expense		$ 190,000
State | Minimum
Income Taxes
Period of net operating losses carryforward			10 years
State | Maximum
Income Taxes
Period of net operating losses carryforward			20 years