General - Additional Information (Details) $ in Thousands	Mar. 31, 2021 USD ($) member_class member representative	Dec. 31, 2020 USD ($)
Number of classes of members | member_class	2
Number of Class A members | member	11
Number of representatives from each Class A member on the board of directors | representative	2
Number of representatives from each Class B member on the board of directors | representative	1
Consolidated assets | $	$ 2,063,058	$ 2,067,644
VIE's
Consolidated assets | $	$ 5,800	$ 5,800