Borrowed Funds - Schedule of Long-Term Borrowings (Detail) - Long-term borrowings - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
FHLB advances, net	$ 2,163,754	$ 1,480,012
Securities sold under agreements to repurchase	350,000	350,000
Subordinated debt, net	291,857	292,414
Other	28	0
Total long-term borrowings	2,805,639	2,122,426
Unamortized prepayment penalties and other purchase accounting adjustments	2,000	2,800
Deferred issuance costs	$ 1,100	$ 1,200