Accumulated Other Comprehensive Income: Accumulated Other Comprehensive Income (Roll-Forward) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Accumulated other comprehensive income [Roll Forward]
Beginning balance	$ 12.1
Other comprehensive loss before reclassifications	(5.2)
Amounts reclassified from other accumulated comprehensive income	1.1	[1]	(4.4)
Ending balance	8.0
Gains (Losses) on Interest Rate Swaps
Accumulated other comprehensive income [Roll Forward]
Beginning balance	(2.4)
Other comprehensive loss before reclassifications	(5.2)
Amounts reclassified from other accumulated comprehensive income	2.0	[1]
Ending balance	(5.6)
Pension and Postretirement Plans
Accumulated other comprehensive income [Roll Forward]
Beginning balance	14.5
Other comprehensive loss before reclassifications	0
Amounts reclassified from other accumulated comprehensive income	(0.9)	[1]
Ending balance	$ 13.6

[1] See separate table below for details about these reclassifications.