Debt (Tables)

12 Months Ended

Dec. 31, 2017

Debt Disclosure [Abstract]

Summary of Debt

At December 31, 2017 and 2016, our long-term debt and interest rates on that debt were as follows (dollars in millions):

	December 31, 2017					December 31, 2016
	Amount		Interest Rate			Amount		Interest rate
Revolving Credit Facility, due August 2021	$	—		—	%	$	—		—	%
Five-Year Term Loan, due August 2021		—		—	%		380.2		2.02	%
Seven-Year Term Loan, due October 2020		—		—	%		630.5		2.40	%
6.50% Senior Notes due March 2018		150.0		6.50	%		150.0		6.50	%
2.45% Senior Notes, net of discount of $0.5 million    as of December 31, 2017 due December 2020		499.5		2.45	%		—		—	%
3.90% Senior Notes, net of discounts of $0.2 million    and $0.2 million as of December 30, 2017 and 2016,    respectively, due June 2022		399.8		3.90	%		399.8		3.90	%
4.50% Senior Notes, net of discount of $1.2 million    a $1.4 million as of December 30, 2017 and 2016,    respectively, due November 2023		698.8		4.50	%		698.6		4.50	%
3.65% Senior Notes, net of discount of $0.8 million    and $0.9 million as of December 31, 2017 and 2016,    respectively, due September 2024		399.2		3.65	%		399.1		3.65	%
3.40% Senior Notes, net of discount of $1.6 million    as of December 31, 2017 due December 2027		498.4		3.40	%		—		—	%
Total		2,645.7		3.80	%		2,658.2		3.54	%
Less current portion		150.0		6.50	%		25.8		2.11	%
Less unamortized debt issuance costs		15.3					12.5
Total long-term debt	$	2,480.4		3.64	%	$	2,620.0		3.57	%