Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments And Contingencies Disclosure [Abstract]

Schedule of Long-term Commitments

The following is a schedule of future payments under PPAs, minimum lease payments with non-cancelable lease terms in excess of one year, and other net purchase obligations/commitments at December 31, 2016:

					Long-term Service
	Purchased		Operating		Agreements/Capital		Clause Recoverable
(millions)	Power		Leases		Projects		Commitments		Total
Year ended December 31:
2017	$	10.7	$	7.0	$	68.8	$	398.5	$	485.0
2018		10.1		3.5		11.1		231.0		255.7
2019		0.0		2.1		11.8		186.2		200.1
2020		0.0		2.1		6.8		162.9		171.8
2021		0.0		2.2		6.9		132.3		141.4
Thereafter		0.0		37.8		24.4		1,156.6		1,218.8
Total future minimum payments	$	20.8	$	54.7	$	129.8	$	2,267.5	$	2,472.8