SCHEDULE V VALUATION AND QUALIFYING ACCOUNTS (Parenthetical) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Valuation And Qualifying Accounts Disclosure [Line Items]
Valuation allowance, balance reduced as part of sale of business	$ (6.4)	[1]
Allowance for uncollectible reinsurance recoverables [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Valuation allowance, balance reduced as part of sale of business	(6.4)	[1]
Chaucer [Member] | Allowance for uncollectible reinsurance recoverables [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Valuation allowance, balance reduced as part of sale of business	$ (6.4)

[1] Amounts charged to other accounts include foreign exchange gains and losses. Additionally, in 2018 the Company sold its former Chaucer business; accordingly, the $6.4 million balance associated with this business was reduced as part of the sale.