Income taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Deferred tax assets:
Tax credits available for carryforward	$ 3,042	$ 3,042
Net operating loss and other carryforward available	772,095	777,495
Postretirement and pension benefits	52,779	57,002
Deferred loan origination fees/cost	21	2,788
Allowance for credit losses	264,407	265,372
Deferred gains		1,642
Accelerated depreciation	12,514	12,668
FDIC-assisted transaction	152,665	152,665
Intercompany deferred gains	2,477
Lease liability	52,119	55,105
Unrealized net gain on trading and available-for-sale securities	212,359
Difference in outside basis from pass-through entities	46,112	54,781
Other temporary differences	41,992	46,930
Total gross deferred tax assets	1,612,582	1,429,490
Deferred tax liabilities:
Indefinite-lived intangibles	131,174	127,785
Unrealized net gain (loss) on trading and available-for-sale securities		7,146
Right of use assets	46,426	49,307
Deferred loan origination fees/cost	5,092	3,567
Other temporary differences	44,574	45,386
Total gross deferred tax liabilities	227,266	233,191
Valuation allowance	568,966	539,527
Net deferred tax asset	816,350	656,772
PR
Deferred tax assets:
Tax credits available for carryforward	261	261
Net operating loss and other carryforward available	119,891	112,331
Postretirement and pension benefits	52,779	57,002
Deferred loan origination fees/cost	21	2,788
Allowance for credit losses	233,382	233,500
Deferred gains		1,642
Accelerated depreciation	5,246	5,246
FDIC-assisted transaction	152,665	152,665
Intercompany deferred gains	2,477
Lease liability	30,152	31,211
Unrealized net gain on trading and available-for-sale securities	196,221
Difference in outside basis from pass-through entities	46,112	54,781
Other temporary differences	33,701	38,512
Total gross deferred tax assets	872,908	689,939
Deferred tax liabilities:
Indefinite-lived intangibles	78,300	76,635
Unrealized net gain (loss) on trading and available-for-sale securities		4,329
Right of use assets	27,927	29,025
Deferred loan origination fees/cost	1,431	0
Other temporary differences	43,044	43,856
Total gross deferred tax liabilities	150,702	153,845
Valuation allowance	134,495	128,557
Net deferred tax asset	587,711	407,537
US
Deferred tax assets:
Tax credits available for carryforward	2,781	2,781
Net operating loss and other carryforward available	652,204	665,164
Postretirement and pension benefits	0	0
Deferred loan origination fees/cost	0	0
Allowance for credit losses	31,025	31,872
Deferred gains		0
Accelerated depreciation	7,268	7,422
FDIC-assisted transaction	0	0
Intercompany deferred gains	0
Lease liability	21,967	23,894
Unrealized net gain on trading and available-for-sale securities	16,138
Difference in outside basis from pass-through entities	0	0
Other temporary differences	8,291	8,418
Total gross deferred tax assets	739,674	739,551
Deferred tax liabilities:
Indefinite-lived intangibles	52,874	51,150
Unrealized net gain (loss) on trading and available-for-sale securities		2,817
Right of use assets	18,499	20,282
Deferred loan origination fees/cost	3,661	3,567
Other temporary differences	1,530	1,530
Total gross deferred tax liabilities	76,564	79,346
Valuation allowance	434,471	410,970
Net deferred tax asset	$ 228,639	$ 249,235