Borrowings (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014	Dec. 31, 2014 USD ($)
Long-term borrowings [Abstract]
Long-term debt	$ 474.8		$ 400.0
Less: current maturities	26.3		15.0
Long-term debt (noncurrent)	448.5		385.0
Derivative, notional amount	100.0
Derivative liability	$ 2.3		0.2
Senior Notes
Long-term borrowings [Abstract]
Debt term	5 years
Senior Notes | Term Loan due January 2019
Long-term borrowings [Abstract]
Long-term debt	$ 288.8		300.0
Line of Credit | Revolving Credit Facility
Long-term borrowings [Abstract]
Secured revolving credit facility, maximum borrowing capacity	$ 350.0
Debt term	5 years
Line of Credit | Revolving Credit Facility | Revolving Credit Facility due January 2019
Long-term borrowings [Abstract]
Long-term debt	$ 186.0		$ 100.0
Credit Facilities
Long-term borrowings [Abstract]
Debt covenant, EBITDA to interest ratio	3.25
Debt covenant, debt to EBITDA	3.25
Credit Facilities | Minimum
Long-term borrowings [Abstract]
commitment fee percentage	0.20%
Credit Facilities | Maximum
Long-term borrowings [Abstract]
commitment fee percentage	0.40%
Credit Facilities | Weighted Average
Long-term borrowings [Abstract]
commitment fee percentage	0.37%	0.25%
Credit Facilities | LIBOR
Long-term borrowings [Abstract]
Interest rate at period end	2.27%	1.66%
Credit Facilities | LIBOR | Minimum
Long-term borrowings [Abstract]
Basis spread on variable rate	1.25%
Credit Facilities | LIBOR | Maximum
Long-term borrowings [Abstract]
Basis spread on variable rate	2.25%