Combined Guarantor Subsidiaries - Revenues - Contract Balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019
Change in Contract with Customer, Liability [Roll Forward]
Contract liability	$ 261	$ 265
Completed performance obligation	0	(4)
Contract obligation	0	0
Contract liability	261	261
Contract with Customer, Liability [Abstract]
Contract liability	261	265	$ 261
Expected Settlement Period
2019			(99)
2020			(54)
2021			(54)
2022			(54)
Guarantor Subsidiaries
Change in Contract with Customer, Liability [Roll Forward]
Contract liability	79	79
Completed performance obligation	0	0
Contract obligation	0	0
Contract liability	79	79
Contract with Customer, Liability [Abstract]
Contract liability	$ 79	$ 79	79
Expected Settlement Period
2019			(19)
2020			(20)
2021			(20)
2022			$ (20)