Commitments and Contingencies - Balance and Total Unfunded Commitments Related to Investment in Low Income Housing Partnerships (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Investments in low income housing partnerships	$ 4,928	$ 1,719
Unfunded commitments to fund investments for low income housing partnerships	$ 2,362	$ 70