Note Fair value measurement (Assets measured at fair value on nonrecurring basis) (Detail) - Nonrecurring - Fair Value by Asset Class [Domain] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Fair Value
Loans	[1]	$ 13,147	$ 29,826
Other real estate	[2]	8,035	14,397
Other foreclosed assets	[2]	1,283	2,045
Total		22,465	46,268
Loans - write-down	[1]	(3,316)	(13,766)
Other real estate owned - write down	[2]	(1,889)	(3,116)
Other foreclosed assets - write down	[2]	(118)	(523)
Total assets measured - write down		(5,323)	(17,405)
Level 1
Fair Value
Loans	[1]	0	0
Other real estate	[2]	0	0
Other foreclosed assets	[2]	0	0
Total		0	0
Level 2
Fair Value
Loans	[1]	0	0
Other real estate	[2]	0	0
Other foreclosed assets	[2]	0	0
Total		0	0
Level 3
Fair Value
Loans	[1]	13,147	29,826
Other real estate	[2]	8,035	14,397
Other foreclosed assets	[2]	1,283	2,045
Total		$ 22,465	$ 46,268

[1] Relates mostly to certain impaired collateral dependent loans. The impairment was measured based on the fair value of the collateral, which is derived from appraisals that take into consideration prices in observed transactions involving similar assets in similar locations, in accordance with the provisions of ASC Section 310-10-35 . Costs to sell are excluded from the reported fair value amount .

[2] Represents the fair value of foreclosed real estate and other collateral owned that were written d own to their fair value. Costs to sell are excluded from the reported fair value amount