Schedule II - Condensed Financial Information of Registrant - Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2021	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues
Total realized and unrealized investment gains and net investment income	$ (151.2)	$ 199.8	$ 77.4	$ 186.5	$ 263.9	$ 463.7	$ 312.5	$ 278.9	$ 282.5
Other revenues	29.3	33.2	31.8	56.9	88.7	121.9	151.2	0.0	0.0
Total revenues	398.0	732.6	561.5	488.6	1,050.1	1,782.7	2,180.7	889.7	982.6
Expenses
Net corporate and other expenses	72.1	59.9	55.7	78.9	134.6	194.5	266.6	41.9	36.2
Interest expense	9.6	9.7	9.8	4.9	14.7	24.4	34.0	8.2	8.2
Foreign exchange gains	(27.5)	(16.1)	12.0	(12.4)	(0.4)	(16.5)	(44.0)	5.2	3.6
Total expenses	551.9	793.0	481.8	308.9	790.7	1,583.7	2,135.6	737.8	781.3
Income before income tax (expense) benefit	(153.9)	(60.4)	79.7	179.7	259.4	199.0	45.1	151.9	201.3
Income tax expense	17.1	13.0	(9.6)	(9.8)	(19.4)	(6.4)	10.7	(8.1)	(0.7)
Net income available to SiriusPoint	(136.3)	(44.0)	68.5	169.9	238.4	194.4	58.1	143.5	200.6
Dividends on Series B preference shares	(4.0)	(4.0)	(4.0)	(1.5)	(5.5)	(9.5)	(13.5)	0.0	0.0
Net income (loss) available to SiriusPoint common shareholders	(140.3)	(48.0)	64.5	168.4	232.9	184.9	44.6	143.5	200.6
Net income (loss) available to SiriusPoint common shareholders	$ (140.3)	$ (48.0)	$ 64.5	$ 168.4	$ 232.9	$ 184.9	44.6	143.5	200.6
Parent Company
Revenues
Total realized and unrealized investment gains and net investment income							1.3	0.0	0.0
Other revenues							100.2	0.0	0.0
Equity in earnings of subsidiaries							90.1	169.9	216.9
Total revenues							191.6	169.9	216.9
Expenses
Net corporate and other expenses							109.5	26.4	16.3
Interest expense							34.0	0.0	0.0
Foreign exchange gains							(18.2)	0.0	0.0
Total expenses							125.3	26.4	16.3
Income before income tax (expense) benefit							66.3	143.5	200.6
Income tax expense							(8.2)	0.0	0.0
Net income available to SiriusPoint							58.1	143.5	200.6
Dividends on Series B preference shares							(13.5)	0.0	0.0
Net income (loss) available to SiriusPoint common shareholders							44.6	143.5	200.6
Net income (loss) available to SiriusPoint common shareholders							$ 44.6	$ 143.5	$ 200.6