Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 17,816		$ 16,270
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	0.35%
Other Income [Member]
Related Party Transaction [Line Items]
Investment income generated from mutual funds	$ 346	$ 182
Cash and Cash Equivalents [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	8,874		$ 12,506
Marketable Securities [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 8,941		$ 3,764