Detail of Certain Balance Sheet Accounts - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Provision for long-term contract receivable	$ 49,900	$ 52,500	$ 102,460
Sunrise Powerlink Project [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Provision for long-term contract receivable	$ 49,900	$ 52,500	$ 102,500