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			6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017	Dec. 31, 2017
Cash Flow Noncash Investing And Financing Activities Disclosure Abstract
Loans transferred to other real estate					$ 10,862		$ 62,474
Loans transferred to other property					18,545		15,812
Total loans transferred to foreclosed assets					29,407		78,286
Financed sales of other real estate assets					8,576		7,318
Financed sales of other foreclosed assets					6,885		4,227
Total financed sales of other foreclosed and real estate assets					15,461		11,545
Transfers from loans held-for-sale to loans held-in-portfolio					15,717		1,558
Loans securitized into investment securities	[1]				256,046		348,004
Trades receivables from brokers and counterparties		$ 38,552		$ 60,511	38,552		60,511	$ 7,514
Trades payable to brokers and counterparties		8,569		3,291	8,569		3,291
Receivables from investment maturities					50,000		0
Recognition of mortgage servicing rights on securitizations or asset transfers					4,923		5,839
Interest capitalized on loans subject to the temporary payment moratorium					481		0
Loans booked under the GNMA buy-back option					352,774		221
Loans sold to a joint venture in exchange for an acquisition loan and an equity interest in the joint venture		$ 102,752	[2]	$ 0	$ 102,752	[2]	$ 0

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

[2] Refer to Note 9 for additional information of the Termination Agreement with the FDIC.