Goodwill and Other Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2018
Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	8 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	13 years
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	10 years
Customer Renewal Lists | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	8 years
Customer Renewal Lists | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible assets, years	13 years