Special Purpose Entities - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended		3 Months Ended					3 Months Ended	9 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013 Project	Oct. 31, 2012	Apr. 30, 2013 Moxie Liberty LLC [Member]	Jul. 31, 2013 Moxie Patriot LLC [Member]	Oct. 31, 2013 Moxie Patriot LLC [Member]	Oct. 31, 2013 Moxie Patriot LLC [Member] Notes Receivable [Member]	Oct. 31, 2013 Moxie Patriot LLC [Member] Accrued Interest Receivable on Notes [Member]	Oct. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member]	Oct. 31, 2013 Variable Interest Entity, Primary Beneficiary [Member]	Oct. 31, 2012 Variable Interest Entity, Primary Beneficiary [Member]	Aug. 31, 2013 Gemma Power Inc [Member] Panda Liberty LLC [Member]	Oct. 31, 2013 Joint Venture [Member]	Oct. 31, 2013 Joint Venture [Member]
Variable Interest Entity [Line Items]
Number of natural gas-fired power plant projects under development			2
Prospective amount of loan to Moxie Projects, maximum											$ 10,000,000
Income attributable to the noncontrolling interest										369,000	101,000	783,000		521,000	601,000
Cash received from Panda Liberty in respect of sale of membership interest to third party investor													19,373,000
Cash received from Panda Liberty in respect of development success fees													14,245,000
Cash received from Panda Liberty for repayment of notes receivable and accrued interest													5,128,000
Gains on the deconsolidation of variable interest entities			2,444,000		1,120,000	1,324,000
Note receivable from Moxie Patriot								4,498,000	937,000
Company's amount of maximum exposure to loss							5,435,000
Revenue from consolidated joint venture as to consolidated net revenue description	$ 63,452,000	$ 74,486,000	$ 167,964,000	$ 220,794,000										$ 17,486,000	$ 20,589,000