Related Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 19,189,000.000		$ 19,062,000.000
Maximum [Member]
Related Party Transaction [Line Items]
Fund management fee percent	0.25%
Other Income (Expense) [Member]
Related Party Transaction [Line Items]
Investment income generated from mutual funds	$ 127,000.000	$ 293,000.000
Cash and Cash Equivalents [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	13,282,000.000		13,282,000.000
Marketable Securities [Member]
Related Party Transaction [Line Items]
Balance with Fund Manager	$ 5,907,000.000		$ 5,780,000.000