Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease expense		$ 3,767	$ 3,781
Short-term lease expense	[1]	17,265	16,571
Lease expense, gross		21,032	20,352
Less: Sublease income		329	259
Total lease expense		$ 20,703	$ 20,093
Minimum [Member]
Lessee, Lease, Description [Line Items]
Short term lease, lease term		1 month
Maximum [Member]
Lessee, Lease, Description [Line Items]
Short term lease, lease term		1 year

[1] Short-term lease expense includes all leases with lease terms ranging from less than one month to one year. Short-term leases include, among other things, construction equipment rented on an as-needed basis as well as temporary housing.