Accounts Receivable Accounts Receivable (Details) $ in Thousands, £ in Millions	Dec. 31, 2015 GBP (£)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		$ 388,671	$ 363,104
Allowance for doubtful accounts		(6,213)	(5,826)	$ (3,755)	$ (2,693)
Accounts receivable, net		382,458	357,278
Accounts receivable - trade [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		339,100	304,087
Accounts receivable - grants from outside parties [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		22,997	32,076
Accounts receivable - insurance and other third party claims [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total accounts receivable		26,574	$ 26,941
Freightliner [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, net	£ 64.8	$ 95,500