Income taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Deferred tax assets:
Tax credits available for carryforward	$ 3,042	$ 3,042
Net operating loss and other carryforward available	762,385	777,495
Postretirement and pension benefits	50,997	57,002
Deferred loan origination fees/cost	20	2,788
Allowance for credit losses	274,725	265,372
Deferred gains		1,642
Accelerated depreciation	12,613	12,668
FDIC-assisted transaction	152,665	152,665
Intercompany deferred gains	1,829
Lease liability	49,707	55,105
Unrealized net loss on trading and available-for-sale securities	317,394
Difference in outside basis from pass-through entities	42,459	54,781
Other temporary differences	41,235	46,930
Total gross deferred tax assets	1,709,071	1,429,490
Deferred tax liabilities:
Indefinite-lived intangibles	133,395	127,785
Unrealized net gain (loss) on trading and available-for-sale securities		7,146
Right of use assets	44,093	49,307
Deferred loan origination fees/cost	4,080	3,567
Other temporary differences	39,633	45,386
Total gross deferred tax liabilities	221,201	233,191
Valuation allowance	582,663	539,527
Net deferred tax asset	905,207	656,772
PR
Deferred tax assets:
Tax credits available for carryforward	261	261
Net operating loss and other carryforward available	121,840	112,331
Postretirement and pension benefits	50,997	57,002
Deferred loan origination fees/cost	20	2,788
Allowance for credit losses	240,578	233,500
Deferred gains		1,642
Accelerated depreciation	5,246	5,246
FDIC-assisted transaction	152,665	152,665
Intercompany deferred gains	1,829
Lease liability	28,747	31,211
Unrealized net loss on trading and available-for-sale securities	291,285
Difference in outside basis from pass-through entities	42,459	54,781
Other temporary differences	33,017	38,512
Total gross deferred tax assets	968,944	689,939
Deferred tax liabilities:
Indefinite-lived intangibles	79,617	76,635
Unrealized net gain (loss) on trading and available-for-sale securities		4,329
Right of use assets	26,499	29,025
Deferred loan origination fees/cost	574	0
Other temporary differences	38,104	43,856
Total gross deferred tax liabilities	144,794	153,845
Valuation allowance	138,219	128,557
Net deferred tax asset	685,931	407,537
US
Deferred tax assets:
Tax credits available for carryforward	2,781	2,781
Net operating loss and other carryforward available	640,545	665,164
Postretirement and pension benefits	0	0
Deferred loan origination fees/cost	0	0
Allowance for credit losses	34,147	31,872
Deferred gains		0
Accelerated depreciation	7,367	7,422
FDIC-assisted transaction	0	0
Intercompany deferred gains	0
Lease liability	20,960	23,894
Unrealized net loss on trading and available-for-sale securities	26,109
Difference in outside basis from pass-through entities	0	0
Other temporary differences	8,218	8,418
Total gross deferred tax assets	740,127	739,551
Deferred tax liabilities:
Indefinite-lived intangibles	53,778	51,150
Unrealized net gain (loss) on trading and available-for-sale securities		2,817
Right of use assets	17,594	20,282
Deferred loan origination fees/cost	3,506	3,567
Other temporary differences	1,529	1,530
Total gross deferred tax liabilities	76,407	79,346
Valuation allowance	444,444	410,970
Net deferred tax asset	$ 219,276	$ 249,235