Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Operating lease expense	$ 4,047	$ 11,749
Short-term lease expense	17,786	50,843
Lease expense, gross	21,833	62,592
Less: Sublease income	263	784
Total lease expense	$ 21,570	$ 61,808
Maximum [Member]
Lessee, Lease, Description [Line Items]
Short-term lease, lease term		1 year
Minimum [Member]
Lessee, Lease, Description [Line Items]
Short-term lease, lease term		1 month