Leases (Summary of Total Lease Cost) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Leases
Operating lease cost	$ 83,461	$ 80,091	$ 166,656	$ 158,905
Short-term operating lease cost	941	1,546	2,725	3,604
Variable operating lease cost	20,776	18,885	41,109	37,263
Sublease income	(1,187)	(976)	(2,362)	(1,933)
Total lease cost	$ 103,991	$ 99,546	$ 208,128	$ 197,839