Borrowings - Summary of Federal Home Loan Bank Advances (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Federal Home Loan Bank Advances [Line Items]
Total Federal Home Loan Bank advances	$ 389,620	$ 324,373
Federal Home Loan Bank Line of Credit Advances [Member]
Federal Home Loan Bank Advances [Line Items]
Total Federal Home Loan Bank advances	$ 127,000	$ 311,223
Total Federal Home Loan Bank advances, Weighted Average Rate	0.85%	1.79%
Federal Home Loan Bank Fixed Rate Term Advances [Member]
Federal Home Loan Bank Advances [Line Items]
Total Federal Home Loan Bank advances	$ 262,570	$ 13,095
Total Federal Home Loan Bank advances, Weighted Average Rate	0.83%	2.80%
Total Federal Home Loan Bank advances, Weighted Average Term in Years	6 months	2 years 8 months 12 days
Total Principal Outstanding [Member]
Federal Home Loan Bank Advances [Line Items]
Total Federal Home Loan Bank advances	$ 389,570	$ 324,318
Merger Purchase Accounting Adjustment [Member]
Federal Home Loan Bank Advances [Line Items]
Total Federal Home Loan Bank advances	$ 50	$ 55