Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating lease expense	$ 14,547	$ 15,854
Short-term lease expense	87,969	72,562
Lease expense, gross	102,516	88,416
Less: Sublease income	1,026	1,077
Total lease expense	$ 101,490	$ 87,339
Minimum
Lessee, Lease, Description [Line Items]
Short term lease, lease term	1 month
Maximum
Lessee, Lease, Description [Line Items]
Short term lease, lease term	1 year