Loans - Summary of Information Concerning Loan Portfolio by Collateral Types (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Receivables with Imputed Interest [Line Items]
Total loans excluding purchased credit deterioated loans	$ 11,876,909	$ 11,848,475
Total PCD loans	150,322	135,468
Total loans	12,027,231	11,983,943
Allowance for credit losses for loans that are not PCD loans	(140,803)	(40,429)
Net Loans	11,868,498	11,943,288
Allowance for loan losses for loans that are not PCD loans [Member]
Receivables with Imputed Interest [Line Items]
Real estate loans, Residential	2,537,240	2,512,544
Real estate loans, Commercial	6,391,975	6,325,108
Land, development and construction	929,014	999,923
Total real estate	9,858,229	9,837,575
Consumer and other loans	235,200	247,307
Loans before unearned fees and deferred cost	11,871,955	11,843,956
Net unearned fees and costs	4,954	4,519
PCD [Member]
Receivables with Imputed Interest [Line Items]
Real estate loans, Residential	42,779	45,795
Real estate loans, Commercial	92,281	81,576
Land, development and construction	5,447	4,655
Total real estate	140,507	132,026
Consumer and other loans	59	100
Commercial and industrial	9,756	3,342
Allowance for credit losses for PCD loans	(17,930)	(226)
Commercial Industrial and Factored Receivables [Member] | Allowance for loan losses for loans that are not PCD loans [Member]
Receivables with Imputed Interest [Line Items]
Commercial, industrial & factored receivables	$ 1,778,526	$ 1,759,074