Leased Assets and Liabilities (Operating and Finance Lease Assets and Liabilities) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating	$ 172,617	$ 152,554
Finance	11,250	10,683
Total leased assets	183,867	163,237
Current operating lease liabilities	34,091	35,208
Noncurrent operating lease liabilities	148,125	125,294
Accounts payable and accrued liabilities	2,773	2,708
Other noncurrent liabilities	7,589	7,054
Total lease liabilities	$ 192,578	$ 170,264
Maximum
Lessee, Lease, Description [Line Items]
Term of contract	15 years
Option to extend	5 years