Note FDIC loss share asset (Activity in the FDIC loss share indemnification asset) (Detail) - USD ($) $ in Thousands		3 Months Ended				12 Months Ended
		Mar. 31, 2017		Mar. 31, 2016		Dec. 31, 2016
Disclosure Activity In The F D I C Loss Share Indemnification Asset [Abstract]
Beginning Balance		$ 69,334		$ 310,221		$ 310,221
Amortization of loss share indemnification asset		(776)		(4,042)
Credit impairment losses (reversal) to be covered under loss sharing agreements	[1]	148		(2,093)
Reimbursable expenses		921		3,950
Net payment from FDIC under loss-sharing agreements		0		(88,588)
Other adjustments attributable to FDIC loss sharing agreements		(5,550)		0
Ending Balance		64,077		219,448		69,334
Balance due to the FDIC for recoveries on covered assets		(5,284)	[2]	(6,301)	[2]	$ (27,600)
FDIC loss-share asset net		$ 58,793		$ 213,147

[1] Reductions in expected cash flows for ASC 310-30 loans, which may impact the provision for loan losses, may consider reductions in both principal and interest cash flow expectations. The amount covered under the FDIC loss sharing agreements for interest not collected from borrowers is limited under the agreements (approximately 90 days); accordingly, these amounts are not subject fully to the 80% mirror accounting.

[2] Balance due to the FDIC for recoveries on covered assets for the quarter ended March 31, 2016 amounting to $6.3 million was included in other liablilities in the accompanying consolidated statement of condition (December 31, 2016 - $27.6 million).