Recently Issued Accounting Standards - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended
	Jan. 01, 2020	Mar. 31, 2020	Dec. 31, 2019
Cumulative adjustment pursuant to adoption of ASU		$ (1,093)
Troubled debt restructurings, loan amount		11,863
Troubled debt restructuring loans under modified terms, amount		7,215
Non-performing loans		4,648
Off Balance Sheet Credit [Member]
Allowance for credit losses on OBS exposures	$ 6,084
Accounting Standards Update 2016-13 [Member]
Impact of adopting ASC 326	74,608
Cumulative adjustment pursuant to adoption of ASU	47,751	47,751
Retained earnings, deferred tax	15,947
Allowance for credit loss post transaction	115,270		$ 40,652
Purchased credit deteriorated loans, net	170,921
Individually analyzed purchased credit deteriorated loans	31,380
Accrued interest receivable on available-for-sale debt securities		6,058
Accrued Interest receivable on held-to-maturity debt securities		1,536
Allowance for credit losses		$ 10
Accounting Standards Update 2016-13 [Member] | Purchased Credit Deteriorated Loans [Member]
Impact of adopting ASC 326	17,004
Accounting Standards Update 2016-13 [Member] | PCD [Member]
Amortized Cost of asset adjusted to allowance for credit loss	$ 17,230