Shareholders' Equity and Earnings (Loss) Per Common Share - Common Shares Repurchased (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		31 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2020
Shareholders' Equity and Earnings (Loss) Per Common Share
Authorized value of shares for repurchase						$ 1,000.0	$ 500.0
Repurchase and retired common shares	2.3	2.3	14.2	2.9	23.3
Repurchase and retired common shares, Value	$ 54.0	$ 68.9	$ 361.0	$ 88.1	$ 623.5
Average purchase price	$ 23.35	$ 29.73	$ 25.49	$ 29.99	$ 26.74