Goodwill and Other Intangible Assets - Summary of Core Deposit Intangibles (Detail) - Core deposit intangibles $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Finite-Lived Intangible Assets [Line Items]
Core deposit intangibles, beginning balance	$ 37,163
Core deposit intangibles, additions	0
Core deposit intangibles, reductions/amortization	0
Core deposit intangibles, ending balance	37,163
Accumulated amortization, beginning balance	(13,606)
Accumulated amortization, additions	0
Accumulated amortization, reductions/amortization	(5,724)
Accumulated amortization, ending balance	(19,330)
Core deposit intangibles, net, beginning balance	23,557
Core deposit intangibles, net, additions	0
Core deposit intangibles, net, reductions/amortization	(5,724)
Core deposit intangibles, net, ending balance	$ 17,833