CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other comprehensive income (loss), tax
Tax benefit (expense) on gains (losses) on changes in unrealized fair value of derivatives designated as cash flow hedges	[1]			$ 45.9
Pension and other postretirement plans adjustments:
Tax benefit (expense) on net unamortized gain (loss) incurred	[2]	$ 0.3	$ 8.5	8.3
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax	[3]	(0.2)	(0.3)	(0.9)
Tax expense on prior service cost incurred	[4]	(4.9)	(6.0)	$ (2.1)
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax	[5]	0.3
Tax expense on net curtailment and settlements cost incurred	[6]	$ 2.6	$ 3.5

[1] Presented net of income tax benefit of $45.9 million for the year ended December 31, 2013.

[2] Presented net of income tax benefit of $0.3 million for the year ended December 31, 2015, net of income tax benefit of $8.5 million for the year ended December 31, 2014, and net of income tax expense of $8.3 million for the year ended December 31, 2013

[3] Presented net of income tax expense of $0.2 million, $0.3 million, and $0.9 million during the years ended December 31, 2015, 2014, and 2013, respectively.

[4] Presented net of income tax expense of $4.9 million, $6.0 million, and $2.1 million during the years ended December 31, 2015, 2014, and 2013, respectively.

[5] Presented net of income tax benefit of $0.3 million for the year ended December 31, 2015.

[6] Presented net of income tax expense of $2.6 million and $3.5 million for the years ended December 31, 2015 and 2014, respectively.