Debt Financing (Details) - USD ($)	Jun. 19, 2019	Jun. 30, 2019	Dec. 31, 2018	Oct. 19, 2018
Domestic Line of Credit
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding		$ 2,550,000	$ 5,028,000
Line of credit, remaining borrowing capacity		200,000	443,000
Cash Collateral Security Agreement [Member] | Standby Letters of Credit
Line of Credit Facility [Line Items]
Cash collateral, percentage of face amount of outstanding standby letters of credit	105.00%
Letters of credit, amount outstanding		463,000
Restricted cash		502,000
Cash Collateral Security Agreement [Member] | Standby Letters of Credit | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)	2.50%
U.S. Domestic Credit Facility | Revolving Credit Facility
Line of Credit Facility [Line Items]
Letters of credit, amount outstanding		$ 0	$ 0
Restricted cash	$ 2,750,000
Line of credit, maximum borrowing capacity	$ 2,750,000			$ 5,500,000
U.S. Domestic Credit Facility | Revolving Credit Facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (as percent)	3.00%