Balance Sheet Components - Additional Information (Detail) (USD $)	1 Months Ended		12 Months Ended
	Jul. 31, 2010	Jan. 31, 2010	Dec. 31, 2012 Security	Dec. 31, 2011 Security	Dec. 31, 2010
Additional distributions	$ 3,626,000	$ 3,626,000
Number of securities			51	71
Aggregate capital leases			141,923,000	132,245,000
Accumulated depreciation			42,272,000	33,790,000
Impairment charges related to property, plant and equipment			7,029,000
Amortization expense			$ 23,575,000	$ 19,064,000	$ 13,632,000