Acquisitions (Details) - USD ($) $ in Millions			12 Months Ended
	Aug. 31, 2021	Aug. 06, 2021	Dec. 31, 2023	Dec. 31, 2022
Business Acquisition [Line Items]
Goodwill and intangible assets, acquisitions			$ 11.0	$ 8.0
Westpac Lenders Mortgage Insurance Limited
Business Acquisition [Line Items]
Term of business exclusivity agreement	10 years
Somerset
Business Acquisition [Line Items]
Goodwill and intangible assets, acquisitions		$ 350.1