Goodwill and Other Intangible Assets - Total Amortizing Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 138,421	$ 1,070,027
Accumulated Amortization	109,387	1,022,960
Net Carrying Amount	29,034	47,067
Core Deposit [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	131,664	887,459
Accumulated Amortization	105,802	843,572
Net Carrying Amount	25,862	43,887
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	6,757	182,568
Accumulated Amortization	3,585	179,388
Net Carrying Amount	$ 3,172	$ 3,180