Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Mar. 31, 2013 Internal Revenue Service (IRS) [Member] Settlement with Taxing Authority [Member]	Dec. 31, 2009 Internal Revenue Service (IRS) [Member] Settlement with Taxing Authority [Member]	Mar. 31, 2013 Prior Period Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Depreciation and Other Amortization	$ 27,307	$ 32,009				$ 1,640
Period to carry back net operating losses				up to 5 years
IRS Tax Refund					40,418
Refunds in excess are required to be reviewed by Joint Committee on Taxation				2,000
Agreed Refund Adjustment to Taxable Income				13,700
Taxes Owed				4,806
Accrued Interest				490
Preferred Stock Distributions Taxable as Capital Gain				$ 8,238
Long Term Capital Gains as a Percentage of Distributions			35.42%
Return Of Capital as a Percentage of Distributions			64.58%