Revenue Recognition - Lease Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Sales-type lease revenue:
Revenue at lease commencement	$ 1,208	$ 2,291	$ 3,358	$ 4,167
Interest income	14	206	178	716
Total sales-type lease revenue	1,222	2,497	3,536	4,883
Operating lease revenue	13,558	16,385	41,487	50,269
Total lease revenue	14,780	$ 18,882	45,023	$ 55,152
Sales-type lease receivable	$ 10,600		$ 10,600		$ 6,500