Regulatory Assets 2 Narrative (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Regulatory Assets Summary [Abstract]
Recovered through rates	$ 36.6	$ 48.8
Not in rates	$ 20.8
Recovery period minimum	3	7
Recovery period maximum	84	84

Amount of regulatory costs not yet approved by the regulatory authority.

No definition available.

Name:	us-gaap_AmountOfRegulatoryCostsNotYetApproved
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant