Commitments and Contingencies - Years In Which Commitments are Expected to be Paid (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Commitments to contribute capital to small business investment companies and CRA-related loan pools	$ 54,785	$ 55,499
2020
Other Commitments [Line Items]
Commitments to contribute capital to small business investment companies and CRA-related loan pools	27,393
2021
Other Commitments [Line Items]
Commitments to contribute capital to small business investment companies and CRA-related loan pools	$ 27,392