(4) Investment in Sunrise Energy (Detail) - Condensed Statement of Operations (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Revenue	$ 37,114		$ 44,628		$ 106,245		$ 116,153
Expenses	(27,844)		(25,112)		(78,153)		(72,837)
Net income	6,190	[1]	12,556	[1]	18,801	[1]	27,289	[1]
Sunrise Energy
Revenue					1,671		3,112
Expenses					(1,573)		(1,564)
Net income					$ 98		$ 1,548

[1] *There is no material difference between net income and comprehensive income.