Subsequent Events - Additional Information (Detail) (Subsequent Event [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Oct. 23, 2012	Oct. 22, 2012
Subsequent Event [Line Items]
Public offering interest rate		7.50%
Public offering issued price	98.277%
Yield to maturity rate	7.75%
Senior Notes due 2022 [Member]
Subsequent Event [Line Items]
Value of public offering		300
Senior Notes due 2014 [Member]
Subsequent Event [Line Items]
Outstanding aggregate principal amount	200