Derivative Financial Instruments Foreign Currency Exchange Rate Risk (Details) £ in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2015 GBP (£)	Mar. 31, 2015 USD ($)	Mar. 31, 2018 GBP (£)	Mar. 31, 2018 USD ($)	Mar. 25, 2015 GBP (£)	Mar. 25, 2015 USD ($)
Derivative [Line Items]
Foreign subsidiaries third-party debt denominated in local currencies | $						$ 1,200.0
Foreign Exchange Forward [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion | $	$ 0.2	$ 0.1
Existing net gains expected to be realized within the next 12 months | $	$ 0.7
British Pound Foreign Currency Forward Contract 1 [Member]
Derivative [Line Items]
Effective Date	Mar. 25, 2015
Settlement Date	Mar. 31, 2020
Notional Amount					£ 60,000
Exchange Rate					1.51	1.51
British Pound Foreign Currency Forward Contract 2 [Member]
Derivative [Line Items]
Effective Date	Mar. 25, 2015
Settlement Date	Mar. 31, 2020
Notional Amount					£ 60,000
Exchange Rate					1.50	1.50
British Pound Foreign Currency Forward Contract 3 [Member]
Derivative [Line Items]
Effective Date	Jun. 30, 2015
Settlement Date	Mar. 31, 2020
Notional Amount					£ 2,035
Exchange Rate					1.57	1.57
British Pound Foreign Currency Forward Contract 4 [Member]
Derivative [Line Items]
Effective Date	Sep. 30, 2015
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,846
Exchange Rate					1.51	1.51
British Pound Foreign Currency Forward Contract 5 [Member]
Derivative [Line Items]
Effective Date	Dec. 31, 2015
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,873
Exchange Rate					1.48	1.48
British Pound Foreign Currency Forward Contract 6 [Member]
Derivative [Line Items]
Effective Date	Mar. 31, 2016
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,881
Exchange Rate					1.45	1.45
British Pound Foreign Currency Forward Contract 7 [Member]
Derivative [Line Items]
Effective Date	Jun. 30, 2016
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,909
Exchange Rate					1.35	1.35
British Pound Foreign Currency Forward Contract 8 [Member]
Derivative [Line Items]
Effective Date	Sep. 30, 2016
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,959
Exchange Rate					1.33	1.33
British Pound Foreign Currency Forward Contract 9 [Member]
Derivative [Line Items]
Effective Date	Dec. 30, 2016
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,989
Exchange Rate					1.28	1.28
British Pound Foreign Currency Forward Contract 10 [Member]
Derivative [Line Items]
Effective Date	Mar. 31, 2017
Settlement Date	Mar. 31, 2020
Notional Amount					£ 1,975
Exchange Rate					1.30	1.30
British Pound Foreign Currency Forward Contract 11 [Member]
Derivative [Line Items]
Effective Date	Jun. 30, 2017
Settlement Date	Mar. 31, 2020
Notional Amount					£ 2,026
Exchange Rate					1.34	1.34
British Pound Foreign Currency Forward Contract 12 [Member]
Derivative [Line Items]
Effective Date	Oct. 02, 2017
Settlement Date	Mar. 31, 2020
Notional Amount					£ 2,079
Exchange Rate					1.36	1.36
British Pound Foreign Currency Forward Contract 13 [Member]
Derivative [Line Items]
Effective Date	Dec. 29, 2017
Settlement Date	Mar. 31, 2020
Notional Amount					£ 2,111
Exchange Rate					1.39	1.39
British Pound Foreign Currency Forward Contract 14 [Member]
Derivative [Line Items]
Effective Date	Mar. 31, 2018
Settlement Date	Mar. 31, 2020
Notional Amount					£ 2,096
Exchange Rate					1.44	1.44
Freightliner [Member]
Derivative [Line Items]
Cash consideration			£ 492,100	$ 733.0
Intercompany Loan [Member]
Derivative [Line Items]
Long-term Debt, Gross							£ 120,000	$ 181.0
Accrued interest					£ 23,800	$ 33.4