Stockholders' Equity Reclassifications Out of Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	$ (19.2)	[1]	$ (20.8)	[1]
Income before taxes	137.9		140.1
Provision for income taxes	(47.1)		(50.0)
Net income	90.8		90.1
Unfunded Employee Benefit Obligations | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service costs	(1.4)	[2]	(1.6)	[2]
Amortization of actuarial losses	(2.2)	[2]	(0.2)	[2]
Income before taxes	(3.6)		(1.8)
Provision for income taxes	1.4		0.8
Net income	(2.2)		(1.0)
Treasury Lock | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	(1.4)	[3]	(1.4)	[3]
Provision for income taxes	0.6		0.6
Net income	$ (0.8)		$ (0.8)

[1] During the three months ended March 31, 2015 and 2014, we received an interest rebate on a portion of our bank debt, reducing our interest expense $4.1 million and $0.8 million, respectively.

[2] These AOCI components are included in the computation of net pension and postretirement benefit costs. See Note 11, Employee Benefit Plans and Other Postretirement Benefits, for additional information.

[3] This AOCI component is included in interest expense, net. Amount relates to the amortization of the effective portion of treasury lock derivative instruments recorded in AOCI. The net amount of settlement gains or losses on derivative instruments included in AOCI to be amortized over the next 12 months is a net loss of $5.7 million ($3.4 million after tax). For a discussion of treasury lock derivative instrument activity, see Note 13, Derivative Instruments and Hedging Activities, of the Notes to Consolidated Financial Statements in "Part II, Item 8. Financial Statements and Supplementary Data" of our 2014 Annual Report on Form 10-K.