Commitments and Contingencies Commitments and Contingencies (Details)	9 Months Ended
	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loss Contingencies [Line Items]
Loss Contingency, Accrual, Current	$ 6,408,000	$ 6,548,000
Loss Contingency, Accrual, Noncurrent	$ 2,228,000	$ 2,283,000
Number of repair facilities with labor union collective bargaining agreements	2
Loss Contingency, Damages Sought, Value	$ 9,000,000
Gain Contingency, Unrecorded Amount	1,800,000
Loss Contingency Accrual	$ 8,600,000