Related Party Transactions - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Related Party Transaction [Line Items]
Purchase of airplane	$ 2,800,000	$ 65,073,000	$ 78,211,000	$ 87,636,000
Board of Directors Chairman
Related Party Transaction [Line Items]
Brokerage fees paid	80,000
Board of Directors Chairman | Airplane
Related Party Transaction [Line Items]
Related party transaction amount	2,800,000
Board of Directors Chairman | Vehicle
Related Party Transaction [Line Items]
Related party transaction amount	$ 21,000