Miscellaneous Income, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Gains on sales of operating property and equipment	$ 26,093	$ 2,475	$ 3,045
Insurance proceeds/recoveries	1,734	966	0
Contract settlement	1,600	0	55
Foreign currency transaction gains	657	1,236	1,945
Rabbi trust investment income	10,522	2,763	632
Other, net	3,639	5,628	4,479
Total	44,245	13,068	10,156
Gain on sale of a SCS property	$ 24,122	$ 0	$ 0