Income taxes - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Income Taxes
Valuation allowance	$ 450,290,000		$ 513,382,000
Net deferred tax assets (net of valuation allowance)	1,001,093,000		1,009,068,000
Net deferred tax asset	999,744,000		1,007,780,000
Unrecognized tax benefits, accrued interest	2,300,000		2,300,000
Accrual for the payment of penalties	0		0
Total amount of unrecognized tax benefits, that if recognized, would affect effective tax rate	2,900,000		2,900,000
Income tax expense	55,568,000	$ 46,314,000
Interest expense recognized	30,000	56,000
Income tax credits and adjustments	22,900,000
Dividends paid	44,976,000	39,878,000
Prior period correction adjustment
Income Taxes
Income tax credits and adjustments	16,500,000
Prior period correction adjustment | Tax Year 2023
Income Taxes
Income tax expense	5,500,000
Income tax credits and adjustments	5,500,000
Prior period correction adjustment | Tax Year 2022
Income Taxes
Income tax expense	5,400,000
Income tax credits and adjustments	5,400,000
Prior period correction adjustment | Prior to tax year 2022
Income Taxes
Income tax expense	5,600,000
Income tax credits and adjustments	5,600,000
US federal taxes and Puerto Rico taxes
Income Taxes
Income tax credits and adjustments	6,500,000
Dividends paid	50,000,000
Other assets
Income Taxes
Net deferred tax assets (net of valuation allowance)	1,000,000,000.0		1,000,000,000.0
Other liabilities
Income Taxes
Net deferred tax liabilities	1,300,000		1,300,000
BHC | Prior period correction adjustment
Income Taxes
Deferred tax asset valuation allowance	53,700,000
PR
Income Taxes
Valuation allowance	71,380,000		139,347,000
Net deferred tax asset	734,374,000		738,480,000
Income tax expense	55,568,000	46,314,000
Deferred tax asset valuation allowance	2,563,000	$ (4,565,000)
US
Income Taxes
Valuation allowance	378,910,000		374,035,000
Net deferred tax asset	265,370,000		$ 269,300,000
Deferred Tax Assets	$ 644,000,000