Note Income taxes (Components of deferred tax assets and liabilities) (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Tax credits available for carryforward	$ 20,220	$ 18,510
Net operating loss and other carryforward available	1,235,780	1,238,222
Postretirement and pension benefits	93,054	94,741
Allowance for loan losses	634,690	649,107
Accelerated depreciation	10,115	9,828
Difference between the assigned values and the tax basis of assets and liabilities recognized in purchase business combinations	11,344	13,160
Other temporary differences	29,922	31,127
Total gross deferred tax assets	2,048,194	2,068,697
Deferred tax liabilities:
FDIC-assisted transaction	56,331	58,363
Indefinite-lived intangibles	76,576	73,974
Unrealized net gain on trading and available-for-sale securities	20,851	21,335
Other temporary differences	8,959	8,477
Total gross deferred tax liabilities	162,717	162,149
Valuation allowance	669,335	664,287
Net deferred tax asset	1,216,142	1,242,261
Deferred loans origination fees
Deferred tax assets:
Deferred income	6,065	6,622
Deferred gain
Deferred tax assets:
Deferred income	4,676	4,884
Intercompany deferred gains
Deferred tax assets:
Deferred income	$ 2,328	$ 2,496