Leases (Components of Lease Expense) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Leases [Abstract]
Operating lease cost	$ 24,279	$ 49,289
Short-term and month-to-month lease cost	4,960	9,773
Variable lease cost	5,606	9,962
Sublease income	(5,041)	(9,693)
Total net lease cost	$ 29,804	$ 59,331