Leased Assets and Liabilities (Supplemental Cash Flow Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flow Information
Operating cash outflows - operating leases	$ 52,565	$ 44,252	$ 40,599
Operating cash outflows - finance leases	949	700	527
Financing cash outflows - finance leases	4,223	3,096	2,564
Leased assets obtained in exchange for new lease obligations
Operating leases	38,641	87,160	36,260
Finance leases	$ 17,741	$ 4,072	$ 5,715