Changes in Shareholders' Equity (Details 3) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Sep. 30, 2020
Stock repurchase program, authorized amount			$ 2,500.0
Remaining balance under stock repurchase program	$ 1,900.0
Number of shares reacquired through surrender of restricted shares	0.3	0.3
Value of shares reacquired through surrender of restricted shares	$ 57.0	$ 46.0
Number of shares reacquired through net settlement options	0.6	0.6
Aggregate value of shares reacquired through net settlement options	$ 134.0	$ 105.0
Treasury shares reissued for restricted stock award grants and Ameriprise Financial Franchise Advisor Deferred Compensation Plan	0.3	0.5
Open market share repurchases [Member]
Repurchase of common shares (in shares)	1.7	2.5
Repurchase of common shares	$ 363.0	$ 386.0