Revenue Recognition - Contract Balances with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Trade accounts receivable and contract assets, net:
Trade accounts receivable	$ 161,569		$ 161,569		$ 156,648
Contract assets	38,223		38,223		63,758
Allowance for doubtful accounts	(16,413)		(16,413)		(23,777)
Total trade accounts receivable and contract assets, net	183,379		183,379		196,629
Contract liabilities:
Current	89,831		89,831		101,060
Noncurrent	11,048		11,048		10,572
Total contract liabilities	100,879		100,879		111,632
Revenue recognized	7,614	$ 8,290	59,786	$ 47,773
Sales and services
Trade accounts receivable and contract assets, net:
Trade accounts receivable	157,459		157,459		152,632
Leasing
Trade accounts receivable and contract assets, net:
Trade accounts receivable	$ 4,110		$ 4,110		$ 4,016