Loans and Allowance for Loan Losses - Schedule of Average Balance (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable Impaired [Line Items]
Impaired Financing Receivable, Average Recorded Investment, Total	$ 114,193	$ 122,112	$ 121,615	$ 113,927
Commercial [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	20,147	19,960	20,593	20,445
Average Recorded Investment with an allowance recorded	19,866	14,771	17,248	10,393
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	10,964		5,445
Average Recorded Investment with an allowance recorded	2,764	11,307	8,294	7,537
Commercial Real Estate - Other [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	34,073	45,302	39,821	42,209
Average Recorded Investment with an allowance recorded	21,019	24,305	24,806	26,537
Residential [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	2,066	2,303	2,145	2,289
Average Recorded Investment with an allowance recorded	924	863	907	887
Consumer [Member]
Financing Receivable Impaired [Line Items]
Average Recorded Investment with no related allowance	1,166	1,392	1,096	1,617
Average Recorded Investment with an allowance recorded	$ 1,204	$ 1,909	$ 1,260	$ 2,013