Leases (Schedule of Future Minimum Payments Under Capital and Operating Leases) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Capital Leases
2018	$ 3,773
2019	3,641
2020	3,471
2021	2,253
2022	0
Thereafter	0
Total minimum lease payments	13,138
Operating Leases
2018	73,223
2019	31,386
2020	22,260
2021	21,473
2022	11,680
Thereafter	21,796
Total minimum lease payments	181,818
Less amount representing interest (3.00% – 6.00%)	1,335
Present value of minimum lease payments	11,803
Less amount due in one year	3,164	$ 3,703
Total Long-Term Capital Lease Obligation	$ 8,639	$ 11,812
Minimum
Operating Leases
Interest rate (as a percent)	3.00%
Maximum
Operating Leases
Interest rate (as a percent)	6.00%