Quantitative Information Regarding Significant Unobservable Inputs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value Assets And Liabilities Measured On Unobservable Inputs [Line Items]
Bond equivalent yield discount rate	9.50%
Green Bay Option
Fair Value Assets And Liabilities Measured On Unobservable Inputs [Line Items]
Fair Value	$ (11,386)	$ (11,398)	$ (8,030)
Valuation Technique	Black-Scholes Method
Risk adjusted discount rate	7.10%
Volatility rate	35.00%
Annual dividend rate	0.00%
Bond equivalent yield discount rate	0.10%
Green Bay Option | Maximum
Fair Value Assets And Liabilities Measured On Unobservable Inputs [Line Items]
Total term	1 year