Quarterly Financial Data - Summary of Quarterly Result of Operations (Parenthetical) (Detail) (USD $)	3 Months Ended			12 Months Ended		3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Allowance for Doubtful Accounts [Member]	Dec. 31, 2011 Allowance for Doubtful Accounts [Member]	Dec. 31, 2012 Allowance for Doubtful Accounts [Member]	Jan. 13, 2011 CPD NY Energy Corp. [Member]	Mar. 31, 2011 Nouria Energy Ventures [Member]
Quarterly Financial Information [Line Items]
Account receivable reserve						$ 1,781,000	$ 8,802,000	$ 13,980,000
Impairment Charges	3,390,000	17,132,000		13,942,000	20,200,000
Sale lease back and loan transaction									111,621,000	87,047,000
Non-cash allowances for deferred rental revenue		$ 11,043,000	$ 8,715,000