Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation expense	$ 12,700	$ 13,300	$ 34,000	$ 35,900
Amortization expense on finance leases	$ 697		1,895
Property and equipment purchased through accounts payable and accrued liabilities, increased amount			$ 2,000	$ 4,400