Long-Term Debt (Details) - USD ($)	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Long-term Debt Types [Abstract]
Capital leases (year-end weighted average interest rate of 3.6% in 2015 and 3.5% in 2014)	$ 18,900,000		$ 12,100,000	$ 5,500,000
Long Term Debt By Current And Noncurrent [Abstract]
Current maturities of long-term debt	43,300,000		34,100,000
Long-term debt	358,100,000		373,100,000
Total Long-Term Debt	401,400,000		407,200,000
Revolving Facility
Long-term Debt Types [Abstract]
Bank Credit Facility	$ 163,300,000		$ 233,000,000
Interest Rate And Other Disclosures [Abstract]
Average interest rate	1.80%		1.60%
Private Placement
Long-term Debt Types [Abstract]
Bank Credit Facility	$ 92,800,000		$ 99,800,000
Interest Rate And Other Disclosures [Abstract]
Unamortized debt cost	100,000		200,000
Other Non-US Dollar-denominated Facilities
Long-term Debt Types [Abstract]
Bank Credit Facility	$ 14,900,000		$ 9,500,000
Interest Rate And Other Disclosures [Abstract]
Average interest rate	4.00%		6.90%
Captial Lease Interest Rate Information
Long-term Debt Types [Abstract]
Capital leases (year-end weighted average interest rate of 3.6% in 2015 and 3.5% in 2014)	$ 59,500,000		$ 64,900,000
Interest Rate And Other Disclosures [Abstract]
Average interest rate	3.60%		3.50%
Private Placement Notes Series A | Private Placement
Interest Rate And Other Disclosures [Abstract]
Average interest rate	4.60%
Private Placement Notes Series B | Private Placement
Interest Rate And Other Disclosures [Abstract]
Average interest rate	5.20%
Unsecured notes issued in a private placement | Term Loan
Long-term Debt Types [Abstract]
Debt Instrument, Face Amount	$ 70,900,000	$ 75,000,000	$ 0
Long Term Debt By Current And Noncurrent [Abstract]
Total Long-Term Debt	$ 71,000,000
Interest Rate And Other Disclosures [Abstract]
Effective interest rate	2.20%
Unamortized debt cost	$ 200,000