Dispositions (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2019 USD ($)	Dec. 31, 2018 customer	Mar. 31, 2017 customer	Dec. 31, 2017 USD ($) segment
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Discontinued Operations And Other Dispositions [Line Items]
Number of business units | segment				2
Total proceeds				$ 867
Net gain (loss)				$ (324)
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Discontinued Operations And Other Dispositions [Line Items]
Number of customers | customer			265
Virginia [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Discontinued Operations And Other Dispositions [Line Items]
Total proceeds	$ 1,882
Net gain (loss)	$ 405
Virginia [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Discontinued Operations And Other Dispositions [Line Items]
Number of customers | customer		500