Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Dec. 31, 2009 Internal Revenue Service (IRS) [Member] Settlement with Taxing Authority [Member]	Sep. 30, 2013 Internal Revenue Service (IRS) [Member] Settlement with Taxing Authority [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Settlement with Taxing Authority [Member]	Sep. 30, 2013 Prior Period Adjustment [Member]
Summary of Significant Accounting Policies [Line Items]
Depreciation and other amortization	$ 28,604	$ 28,552	$ 84,791	$ 89,138					$ 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								500
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%