Deferred Acquisition Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in deferred acquisition costs
Balance at beginning of year, deferred acquisition costs	$ 3,757.5	$ 3,409.7	$ 3,521.3
Costs deferred during the year	379.0	461.4	457.0
Amortization of deferred acquisition costs	(384.4)	(285.4)	(388.1)
Adjustment related to unrealized (gains) losses on available-for-sale securities and derivative instruments	934.8	171.8	(180.5)
Balance at end of year, deferred acquisition costs	$ 4,686.9	$ 3,757.5	$ 3,409.7