Fair Value Instruments - Additional Information (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value assets, Level 1 to Level 2 transfers, Amount	$ 0	$ 0	$ 0
Fair value, assets, Level 2 to Level 1 transfers, Amount	0	0	0
Fair value, liabilities, Level 1 to Level 2 transfers, Amount	0	0	0
Fair value, liabilities, Level 2 to Level 1 transfers, Amount	0	0	0
Fair value, measurement with unobservable inputs reconciliation, recurring basis, asset transfers into Level 3	0	0	0
Fair value, measurement with unobservable inputs reconciliation, recurring Basis, asset, transfers out of Level 3	0	0	0
Fair Value, measurement with unobservable inputs reconciliation, liability, transfers into Level 3	0	0	0
Fair Value, measurement with unobservable inputs reconciliation, liability, transfers out of Level 3	$ 0	$ 0	$ 0