Goodwill and Other Intangible Assets - Summary of Core Deposit Intangibles (Detail) - Core Deposit Intangibles $ in Thousands	12 Months Ended
	Dec. 31, 2019 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	(7,883)
Accumulated amortization, Additions	0
Accumulated amortization, Reductions/Amortization	(5,723)
Accumulated amortization, Ending balance	(13,606)
Core deposit intangibles, net, Beginning balance	29,280
Core deposit intangibles, net, Additions	0
Core deposit intangibles, net, Reductions/Amortization	5,723
Core deposit intangibles, net, Ending balance	$ 23,557