Note Fair value measurement (Assets measured at fair value on nonrecurring basis) (Detail) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value by Asset Class [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 45,133	$ 30,785
Loans held-for-sale		1,829
Other real estate owned	17,155	18,592
Other Foreclosed Assets	165	66
Total	62,453	51,272
Write-down	(21,142)	(27,077)
Loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Write-down	(16,491)	(22,850)
Loans Held-for-Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Write-down		(296)
Other real estate owned
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Write-down	(4,578)	(3,920)
Other foreclosed assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Write-down	(73)	(11)
Level 1 | Fair Value by Asset Class [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Loans held-for-sale		0
Other real estate owned	0	0
Other Foreclosed Assets	0	0
Total	0	0
Level 2 | Fair Value by Asset Class [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Loans held-for-sale		0
Other real estate owned	0	0
Other Foreclosed Assets	0	0
Total	0	0
Level 3 | Fair Value by Asset Class [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	45,133	30,785
Loans held-for-sale		1,829
Other real estate owned	17,155	18,592
Other Foreclosed Assets	165	66
Total	$ 62,453	$ 51,272