Income taxes - Additional Information (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Income Taxes [Line Items]
Valuation allowance	$ 450,507,000			$ 450,507,000		$ 513,382,000
Net deferred tax assets (net of valuation allowance)	917,793,000			917,793,000		1,009,068,000
Net deferred tax asset	916,315,000			916,315,000		1,007,780,000
Unrecognized tax benefits, accrued interest	2,400,000			2,400,000		2,300,000
Accrual for the payment of penalties	0			0		0
Total amount of unrecognized tax benefits, that if recognized, would affect effective tax rate	3,000,000.0			3,000,000.0		2,900,000
Income tax expense	42,463,000		$ 45,859,000	138,490,000	$ 135,676,000
Interest expense recognized				70,000	79,000
Income tax credits and adjustments		$ 22,900,000		22,900,000
Dividends paid				135,495,000	119,715,000
Prior period correction adjustment
Income Taxes [Line Items]
Income tax credits and adjustments		16,500,000		16,500,000
Prior period correction adjustment | Tax Year 2023
Income Taxes [Line Items]
Income tax credits and adjustments				5,500,000
Prior period correction adjustment | Tax Year 2022
Income Taxes [Line Items]
Income tax credits and adjustments				5,400,000
Prior period correction adjustment | Prior to tax year 2022
Income Taxes [Line Items]
Income tax credits and adjustments				5,600,000
US federal taxes and Puerto Rico taxes
Income Taxes [Line Items]
Income tax credits and adjustments		$ 6,500,000
Other assets
Income Taxes [Line Items]
Net deferred tax assets (net of valuation allowance)	917,800,000			917,800,000		1,000,000,000.0
Other liabilities
Income Taxes [Line Items]
Net deferred tax liabilities	1,500,000			1,500,000		1,300,000
BHC | Prior period correction adjustment
Income Taxes [Line Items]
Deferred tax asset valuation allowance				53,700,000
PR
Income Taxes [Line Items]
Valuation allowance	71,596,000			71,596,000		139,347,000
Net deferred tax asset	666,037,000			666,037,000		738,480,000
Income tax expense	42,463,000		45,859,000	138,490,000	135,676,000
Deferred tax asset valuation allowance	451,000		$ 1,355,000	2,779,000	$ (2,217,000)
US
Income Taxes [Line Items]
Valuation allowance	378,911,000			378,911,000		374,035,000
Net deferred tax asset	250,278,000			250,278,000		$ 269,300,000
Deferred Tax Assets	$ 629,000,000			$ 629,000,000