Note Supplemental disclosure on the consolidated statments of cash flows (Additional disclosures on cash flow information and non-cash activities) (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Cash Flow Noncash Investing And Financing Activities Disclosure Abstract
Loans transferred to other real estate		$ 8,628	$ 6,254
Loans transferred to other property		12,072	9,405
Total loans transferred to foreclosed assets		20,700	15,659
Loans transfered to other assets		5,678	3,178
Financed sales of other real estate assets		3,643	5,250
Financed sales of other foreclosed assets		6,435	4,083
Total financed sales of other foreclosed and real estate assets		10,078	9,333
Transfers from loans held-for-sale to loans held-in-portfolio		7,283	9,215
Loans securitized into investment securities	[1]	92,067	138,242
Trades receivables from brokers and counterparties		32,043	41,683
Trades payable to brokers and counterparties		7,220	53,973
Receivables from investment securities		0	20,000
Recognition of mortgage servicing rights on securitizations or asset transfers		12,084	2,557
Interest capitalized on loans subject to the temporary payment moratorium		0	481
Loans booked under the GNMA buy-back option		5,782	219,487
Capitalization of lease right of use asset		$ 155,727	$ 0

[1] Includes loans securitized into trading securities and subsequently sold before quarter end.