Commitments (Lease Commitments for Leases having Terms of More than One Year) (Details) $ in Thousands	Mar. 31, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	$ 27,015
2019	19,541
2020	17,723
2021	16,096
2022	15,723
Thereafter	69,812
Total	165,910
Property Plant and Equipment, Ground [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	991
2019	1,024
2020	1,024
2021	1,030
2022	1,030
Thereafter	49,649
Total	54,748
Property, Plant and Equipment, Operating [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	17,014
2019	17,217
2020	16,699
2021	15,066
2022	14,693
Thereafter	20,163
Total	100,852
Rental Equipment [Member]
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2018	9,010
2019	1,300
2020
2021
2022
Thereafter
Total	$ 10,310