Transfers and Servicing of Financial Assets (Including Mortgage Banking Activity) - Schedule of Mortgage Servicing Rights at Carrying Value (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	$ 137,774	$ 137,774
Accumulated Amortization	(82,974)	(64,608)
Net Carrying Amount	54,800	73,166
Mortgage servicing rights
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	22,476	13,612
Valuation Allowance	(250)	0
Accumulated Amortization	(6,621)	(4,806)
Net Carrying Amount	$ 15,605	$ 8,806