Summary of Significant Accounting Policies - Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Assets at fair value and gains (losses) recorded
Equipment held for sale	$ 13,899		$ 13,899		$ 23,454
Total losses on equipment held for lease			(1,893)	$ (1,936)
Total losses on equipment held for sale			(3,556)	(6,644)
Total losses on spare parts inventory			(475)
Total losses on assets			(5,924)	(8,580)
Asset write-down	1,995	$ 5,498	5,924	8,580
Additional write-down			2,000
Unamortized debt issuance cost	12,600		12,600
Level 1
Assets at fair value and gains (losses) recorded
Equipment held for lease
Equipment held for sale
Spare parts inventory
Assets at fair value
Nonrecurring
Assets at fair value and gains (losses) recorded
Equipment held for lease	337	1,555	337	1,555
Equipment held for sale	589	7,477	589	7,477
Spare parts inventory	1,731		1,731
Assets at fair value	2,657	9,032	2,657	9,032
Nonrecurring | Level 2
Assets at fair value and gains (losses) recorded
Equipment held for lease	337	1,555	337	1,555
Equipment held for sale	589	7,477	589	7,477
Spare parts inventory	1,731		1,731
Assets at fair value	$ 2,657	$ 9,032	$ 2,657	$ 9,032