UNAUDITED CONDENSED CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Restricted stock units	Common stock	Common stock Restricted stock units	Additional capital in excess of par value	Additional capital in excess of par value Restricted stock units	Retained earnings	AOCI	[1]
Beginning Balances (in shares) at Dec. 31, 2018			238,069,000
Balances at beginning of period at Dec. 31, 2018	$ 6,124.3		$ 47.6		$ 654.6		$ 5,464.1	$ (42.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	512.6						512.6
Other comprehensive income (loss), net of tax	0.4							0.4
Dividends declared	(183.8)						(183.8)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)			830,000
Shares issued upon option exercises	45.0		$ 0.2		44.8
Net shares issued upon vesting of restricted stock units (in shares)				14,000
Net shares issued upon vesting of restricted stock units		$ (1.2)				$ (1.2)
Forfeiture of restricted awards (in shares)			(5,000)
Stock-based compensation expense	43.5				43.5
Common shares repurchased (in shares)			(2,476,000)
Common shares repurchased	(229.8)		$ (0.5)		(87.2)		(142.1)
Ending Balances (in shares) at Mar. 31, 2019			236,432,000
Balances at end of period at Mar. 31, 2019	6,311.0		$ 47.3		654.5		5,650.8	(41.6)
Beginning balances attributable to redeemable non-controlling interests at Dec. 31, 2018	740.3
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	41.4
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(1.3)
Net subscriptions into consolidated T. Rowe Price investment products	85.9
Net reconsolidations (deconsolidations) of T. Rowe Price investment products	20.4
Ending balances attributable to redeemable non-controlling interests at Mar. 31, 2019	886.7
Beginning Balances (in shares) at Dec. 31, 2019			235,214,000
Balances at beginning of period at Dec. 31, 2019	7,102.1		$ 47.0		654.6		6,443.5	(43.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	343.1						343.1
Other comprehensive income (loss), net of tax	(6.1)							(6.1)
Dividends declared	$ (214.7)						(214.7)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)	1,540,694		1,068,000
Shares issued upon option exercises	$ 41.3		$ 0.2		41.1
Net shares issued upon vesting of restricted stock units (in shares)				37,000
Net shares issued upon vesting of restricted stock units		$ (3.0)				$ (3.0)
Stock-based compensation expense	58.3				58.3
Restricted stock units issued as dividend equivalents					0.1		(0.1)
Common shares repurchased (in shares)			(8,334,000)
Common shares repurchased	(887.0)		$ (1.6)		(96.5)		(788.9)
Ending Balances (in shares) at Mar. 31, 2020			227,985,000
Balances at end of period at Mar. 31, 2020	6,434.0		$ 45.6		$ 654.6		$ 5,782.9	$ (49.1)
Beginning balances attributable to redeemable non-controlling interests at Dec. 31, 2019	1,121.0
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	(176.5)
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(17.2)
Net subscriptions into consolidated T. Rowe Price investment products	63.8
Net reconsolidations (deconsolidations) of T. Rowe Price investment products	(20.1)
Ending balances attributable to redeemable non-controlling interests at Mar. 31, 2020	$ 971.0

[1] Accumulated other comprehensive income.