Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 17,615		$ 16,270
Investment income generated from mutual funds	$ 77	$ 12
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	$ 146
Cash and Cash Equivalents [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	8,775		$ 12,506
Marketable Securities [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 8,840		$ 3,764