Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill And Other Intangible Assets [Line Items]
Amortization of core deposit and other intangible assets	$ 14,869	$ 19,490	$ 24,522
Minimum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	5 years
Maximum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	10 years
Core Deposit and Other Intangible Assets [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	7 years
Amortization of core deposit and other intangible assets	$ 15,000	$ 19,000	$ 25,000
Core Deposit and Other Intangible Assets [Member] | Minimum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	3 years
Core Deposit and Other Intangible Assets [Member] | Maximum [Member]
Goodwill And Other Intangible Assets [Line Items]
Estimated useful lives	7 years