Short-Term Borrowings - Summary of Short-Term Borrowings (Detail) - USD ($)	6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Securities sold under repurchase agreements	$ 403,000,000	$ 278,000,000
Federal Home Loan Bank advances	1,280,000,000	2,255,000,000
Federal funds purchased	0	575,000,000
Subordinated notes	121,000,000	108,000,000
Total short-term borrowings	1,804,000,000	3,216,000,000
Short-term advances, overnight maturities	0	0
Short-term advances, swapped to a fixed rate	$ 1,300,000,000	$ 1,500,000,000
Short-term advances, swapped to a fixed rate, percentage bearing fixed interest rate	100.00%	64.50%
FHLB
Debt Instrument [Line Items]
Reduction of higher rate outstanding	$ 225,000,000.0
Hedge termination costs	$ 8,900,000