Low Income Housing Tax Credits and Other Tax Credit Investments - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2021	Dec. 31, 2020
Investments In Affordable Housing Projects [Line Items]
Tax credit investment	$ 74,400,000	$ 59,800,000
Renewable Energy Program
Investments In Affordable Housing Projects [Line Items]
Equity investments	4,200,000	1,200,000
Outstanding investment commitments	$ 0	$ 1,700,000
Low income housing tax credit and other tax credit investments
Investments In Affordable Housing Projects [Line Items]
Tax credit period of benefits	15 years
Operating loss tax benefits period	15 years