Assets and Liabilities for Company's VIEs, Combined by VIE Classifications, that were Included in Consolidated Balance Sheets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Assets:
Restricted cash, cash equivalents and marketable securities	$ 76,537		$ 75,521
Property, plant and equipment, net	1,226,758		1,518,532
Construction-in-process	396,141		370,551
Total assets	2,094,114	[1]	2,314,718	[2]	2,043,328	[3]
Liabilities:
Accounts payable and accrued expenses	98,001		105,112
Billings in excess of costs and estimated earnings on uncompleted contracts	25,408		33,104
Long-term debt	957,323
Other long-term liabilities	5,148		4,253
Total liabilities	1,391,916		1,408,074
Variable Interest Entity, Primary Beneficiary
Assets:
Property, plant and equipment, net	1,162,606		1,477,580
Construction-in-process	253,775		271,859
Variable Interest Entity, Primary Beneficiary | Wholly Owned Subsidiaries with Project Debt
Assets:
Restricted cash, cash equivalents and marketable securities	76,537		75,521
Other current assets	73,135		78,013
Property, plant and equipment, net	966,433		1,019,082
Construction-in-process	248,890		236,101
Other long-term assets	57,337		57,386
Total assets	1,422,332		1,466,103
Liabilities:
Accounts payable and accrued expenses	25,477		13,621
Billings in excess of costs and estimated earnings on uncompleted contracts	1,718
Long-term debt	595,425		476,753
Other long-term liabilities	81,070		84,619
Total liabilities	703,690		574,993
Variable Interest Entity, Primary Beneficiary | Wholly Owned Subsidiaries with PPAs
Assets:
Other current assets	8,766		12,725
Property, plant and equipment, net	196,173		428,498
Construction-in-process	4,885		24,585
Other long-term assets	273		272
Total assets	210,097		466,080
Liabilities:
Accounts payable and accrued expenses	5,393		4,590
Other long-term liabilities	8,386		7,998
Total liabilities	13,779		12,588
Variable Interest Entity, Primary Beneficiary | Less Than Majority-Owned Subsidiaries
Assets:
Construction-in-process	11,121		11,173
Total assets	$ 11,121		$ 11,173

[1] Including unconsolidated investments 2,591 - 2,591

[2] Including unconsolidated investments 2,215 1,542 3,757

[3] Including unconsolidated investments 2,244 2,000 4,244