Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Fair Value, Liabilities Measured on Recurring Basis

Financial liabilities that are measured at fair value on a recurring basis were as follows ($ in millions):

	Quoted Prices in Active Market (Level 1)	Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)	Total
December 31, 2017
Deferred compensation liabilities	—	$	20.9	—	$	20.9
December 31, 2016
Deferred compensation liabilities	—	$	14.8	—	$	14.8

Carrying Values and Fair Values of Financial Instruments

The carrying amounts and fair values of financial instruments as of December 31 were as follows ($ in millions):

	2017				2016
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
Long-term borrowings	$	4,056.2	$	4,051.8	$	3,358.0	$	3,321.4