Reinsurance Reinsurance Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Reinsurance Disclosure [Abstract]
Reinsurance recoverables on paid losses, gross	$ 12,973	$ 14,831
Reinsurance recoverable for unpaid losses	381,356	323,060	$ 241,357	$ 177,039
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	394,329	337,891
Reinsurance Recoverable, Allowance for Credit Loss	1,072	932
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	394,329	337,891
Ceded unearned premiums	44,506	$ 52,736
Credit Risk Reinsurer One [Member]
Reinsurance Disclosure [Abstract]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	95,800
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	95,800
Ceded unearned premiums	9,800
Credit Risk Reinsurer Two [Member]
Reinsurance Disclosure [Abstract]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	46,300
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	46,300
Ceded unearned premiums	5,300
Credit Risk Reinsurer Three [Member]
Reinsurance Disclosure [Abstract]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	37,900
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	37,900
Ceded unearned premiums	4,700
Credit Risk Reinsurer Four [Member]
Reinsurance Disclosure [Abstract]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	30,800
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	30,800
Ceded unearned premiums	4,500
Credit Risk Reinsurer Five [Member]
Reinsurance Disclosure [Abstract]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	24,600
Concentration Risk [Line Items]
Reinsurance recoverables, net of allowance for credit losses of $1,072 in 2025 and $932 in 2024	24,600
Ceded unearned premiums	$ 4,000
Prepaid reinsurance premiums ceded to five reinsurers as a percentage of total ceded unearned premium balance [Member] \| Major Reinsurers [Member] \| Reinsurer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	63.70%
Reinsurance recoverables on paid and unpaid losses from the Company’s five largest reinsurers as percent of total reinsurance recoverables [Member] \| Major Reinsurers [Member] \| Reinsurer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	59.70%

Kinsale Capital Group, Inc. 10-K