Securities - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Dec. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) Security	Dec. 31, 2019 USD ($)	Jun. 30, 2020 Security
Investments Debt And Equity Securities [Abstract]
Gross gains recognized on calls of securities available for sale	$ 13,000,000	$ 11,000,000	$ 21,000,000	$ 13,000,000
Held to maturity gains (losses) recognized on calls of securities	$ 0	$ 0	$ 0	$ 0
Held-to-maturity, securities with unrealized losses, Number of positions | Security	0		0		0
Allowance for credit losses related to available for sale debt securities	$ 0		$ 0