Leases - Finance Leases (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Leases
Finance Leases, net of accumulated amortization	$ 1,400,000	$ 595,000
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net	Property, Plant and Equipment, Net
Finance leases, amortization expense included in operating expenses	$ 159,000	$ 93,000
Obligations under finance leases	$ 0