Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 16,270	$ 14,842
Investment income generated from mutual funds	$ (28)	$ 21
Minimum [Member]
Related Party Transaction [Line Items]
Percentage of stockholders controlling a related party	10.00%	10.00%
Maximum [Member]
Related Party Transaction [Line Items]
Fund management fee percent	0.25%
Other Income [Member]
Related Party Transaction [Line Items]
Investment income generated from mutual funds	$ 203
Cash and Cash Equivalents [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	12,506	$ 11,050
Marketable Securities [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 3,764	$ 3,792