Subsequent Events (Details) (Ironwood [Member], USD $) In Millions, unless otherwise specified	1 Months Ended
	Feb. 28, 2012 MW
Ironwood [Member]
Subsequent Event [Line Items]
Winter rating capacity of plant, in MW	705
Consideration to be paid	$ 87
Net working capital expected to be acquired	4.8
Net amount of debt expected to be assumed	217
Original amount outstanding of debt expected to be assumed	308.5
Interest rate of debt assumed	8.857%
Maturity date of debt assumed	Jan. 01, 2025
Debt outstanding	226
Debt service reserve loans expected to assume	8
Restricted cash reserves expected to acquire	$ 17
Percentage of issued and outstanding membership interests to be acquired	100.00%