Lease Accounting (Major Categories of Operating Lease Portfolio) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating Leased Assets [Line Items]
Total Right of Use Assets, net	$ 184,723	$ 208,929	$ 0
Accrued liabilities, current	29,572	33,016
Other long-term liabilities, non-current	151,680	171,348
Total Lease Liability	181,252	204,364
Transportation Equipment
Operating Leased Assets [Line Items]
Total Right of Use Assets, net	103,396	117,727
Total Lease Liability	107,272
Office Space & Equipment
Operating Leased Assets [Line Items]
Total Right of Use Assets, net	11,914	14,194
Total Lease Liability	12,013
Facilities and Equipment
Operating Leased Assets [Line Items]
Total Right of Use Assets, net	69,413	$ 77,008
Total Lease Liability	$ 61,967