Note Income taxes (Components of deferred tax assets and liabilities) (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Deferred tax assets:
Tax credits available for carryforward	$ 18,510	$ 18,510
Net operating loss and other carryforward available	1,228,008	1,238,222
Postretirement and pension benefits	91,453	94,741
Allowance for loan losses	621,197	649,107
Accelerated depreciation	10,507	9,828
Difference between the assigned values and the tax basis of assets and liabilities recognized in purchase business combinations	12,477	13,160
Other temporary differences	33,681	31,127
Total gross deferred tax assets	2,026,321	2,068,697
Deferred tax liabilities:
FDIC-assisted transaction	57,612	58,363
Indefinite-lived intangibles	76,897	73,974
Unrealized net gain on trading and available-for-sale securities	23,007	21,335
Other temporary differences	9,682	8,477
Total gross deferred tax liabilities	167,198	162,149
Valuation allowance	673,616	664,287
Net deferred tax asset	1,185,507	1,242,261
Deferred loans origination fees
Deferred tax assets:
Deferred income	5,807	6,622
Deferred gain
Deferred tax assets:
Deferred income	4,469	4,884
Intercompany deferred gains
Deferred tax assets:
Deferred income	$ 212	$ 2,496