Investments - Other Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Summarized financial information of unconsolidated entities
Total assets	$ 305,046.7	$ 290,867.0
Total liabilities	293,836.1	280,587.2
Total stockholders' equity	10,961.7	10,017.8	$ 12,140.5	$ 16,617.3
Total revenues	13,665.8	17,536.1	14,427.8
Net income (loss)	670.1	4,797.5	1,627.0
Other Types of Investments
Cash surrender value of company owned life insurance	1,186.3	1,115.6
Certain sponsored investment funds carried at fair value	576.9	617.8
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Summarized financial information of unconsolidated entities
Total assets	215,978.7	209,546.0
Total liabilities	100,865.3	81,160.9
Total stockholders' equity	115,113.4	128,385.1
Total revenues	12,449.3	44,974.8	21,751.9
Net income (loss)	(2,674.2)	34,322.7	15,732.5
Our share of net income of unconsolidated entities	314.9	302.2	$ 406.6
Net Investment in unconsolidated entities
Summarized financial information of unconsolidated entities
Net investment in unconsolidated entities	$ 3,488.7	$ 2,767.9