Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 113,669	$ 104,007
Short-term and month-to-month lease cost	21,862	19,267
Variable lease cost	18,718	20,582
Sublease income	(18,508)	(20,108)
Total net lease cost	$ 135,741	$ 123,748