Goodwill and Intangibles - Summary of Other Intangible Assets (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 32,504	$ 33,861
Accumulated Amortization	(10,067)	(10,153)
Net Intangible Assets	22,437	23,708
Core deposits
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	10,658	13,128
Accumulated Amortization	(4,263)	(5,630)
Net Intangible Assets	$ 6,395	$ 7,498
Amortization Period	10 years	10 years
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 17,561	$ 17,561
Accumulated Amortization	(4,214)	(2,612)
Net Intangible Assets	$ 13,347	$ 14,949
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	7 years	7 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	15 years	15 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 221	$ 1,006
Accumulated Amortization	(57)	(728)
Net Intangible Assets	$ 164	$ 278
Amortization Period	5 years
Non-compete agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period		6 months
Non-compete agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period		3 years
Loan servicing rights
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 2,132	$ 1,708
Accumulated Amortization	(1,191)	(1,067)
Net Intangible Assets	$ 941	$ 641
Loan servicing rights | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years	10 years
Loan servicing rights | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	30 years	30 years
Favorable lease asset
Finite-Lived Intangible Assets [Line Items]
Gross Intangible Assets	$ 1,932	$ 458
Accumulated Amortization	(342)	(116)
Net Intangible Assets	$ 1,590	$ 342
Favorable lease asset | Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 months	10 months
Favorable lease asset | Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization Period	18 years	15 years