Summary of Debt, Net of Discounts (Parenthetical) (Detail) (Revolving Credit Facilities, USD $) In Thousands, unless otherwise specified					12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011		Dec. 31, 2011 Collateralized Debt Obligations
Debt Instrument [Line Items]
Principal amount	$ 125,000	[1]	$ 89,600	[1]	$ 42,000
Expiration date					2012-06

[1] Our $42 million collateralized revolving credit facility expired in June 2012.