Leases (Narrative) (Details) - Sheboygan Falls Energy Facility [Member] - WPL [Member]	12 Months Ended
	Dec. 31, 2005 lease_renewal_period_option
Leases [Line Items]
Capital lease, agreement term	20 years
Capital leases, renewal options (in number of renewal periods)	2
Capital lease asset amortization term	20 years