Leases (Breakdown of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Leases
Operating lease cost	$ 17,878	$ 20,547
Amortization of leased assets	7,510	3,996
Interest on lease liabilities	800	389
Short-term lease cost	9,090	7,187
Sublease income	(559)	(904)
Lease expense	$ 34,719	$ 31,215