UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Restricted shares	Restricted stock units	Common stock	Common stock Restricted shares	Common stock Restricted stock units	Additional capital in excess of par value	Additional capital in excess of par value Restricted shares	Additional capital in excess of par value Restricted stock units	Retained earnings	AOCI	[1]
Beginning balance (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	1,586.0									1,586.0
Other comprehensive income (loss), net of tax	(6.7)										(6.7)
Dividends declared	(549.9)									(549.9)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				2,277,000
Shares issued upon option exercises	119.3			$ 0.4			118.9
Restricted shares issued, net of shares withheld for taxes (in shares)					7,000	51,000
Restricted shares issued, net of shares withheld for taxes		$ (0.1)	$ (2.6)					$ (0.1)	$ (2.6)
Forfeiture of restricted awards (in shares)				(10,000)
Stock-based compensation expense	136.2						136.2
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(5,692,000)
Common shares repurchased	(566.7)			$ (1.1)			(252.5)			(313.1)
Ending balance (in shares) at Sep. 30, 2019				234,702,000
Balances at end of period at Sep. 30, 2019	6,839.8			$ 46.9			654.6			6,187.0	(48.7)
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	69.0
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	17.7
Net subscriptions into consolidated T. Rowe Price investment products	392.7
Net deconsolidations of T. Rowe Price investment products	(81.4)
Ending balances attributable to redeemable non-controlling interests at Sep. 30, 2019	1,102.9
Beginning balance (in shares) at Jun. 30, 2019				235,518,000
Balances at beginning of period at Jun. 30, 2019	6,579.1			$ 47.1			654.6			5,915.9	(38.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	545.9									545.9
Other comprehensive income (loss), net of tax	(10.2)										(10.2)
Dividends declared	(182.7)									(182.7)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				782,000
Shares issued upon option exercises	36.5			$ 0.1			36.4
Restricted shares issued, net of shares withheld for taxes (in shares)					0
Restricted shares issued, net of shares withheld for taxes		0.0						$ 0.0
Net shares issued upon vesting of restricted stock units (in shares)						18,000
Net shares issued upon vesting of restricted stock units			(1.2)						(1.2)
Forfeiture of restricted awards (in shares)				(3,000)
Stock-based compensation expense	45.5						45.5
Restricted stock units issued as dividend equivalents	0.0						0.0			0.0
Common shares repurchased (in shares)				(1,613,000)
Common shares repurchased	(173.1)			$ (0.3)			(80.7)			(92.1)
Ending balance (in shares) at Sep. 30, 2019				234,702,000
Balances at end of period at Sep. 30, 2019	6,839.8			$ 46.9			654.6			6,187.0	(48.7)
Beginning balances attributable to redeemable non-controlling interests at Jun. 30, 2019	1,012.3
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	(0.8)
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	17.4
Net subscriptions into consolidated T. Rowe Price investment products	181.1
Net deconsolidations of T. Rowe Price investment products	(72.3)
Ending balances attributable to redeemable non-controlling interests at Sep. 30, 2019	1,102.9
Beginning balance (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	1,589.3									1,589.3
Other comprehensive income (loss), net of tax	0.3										0.3
Dividends declared	$ (635.3)									(635.3)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)	2,555,527			1,856,000
Shares issued upon option exercises	$ 83.2			$ 0.4			82.8
Restricted shares issued, net of shares withheld for taxes (in shares)					8,000	60,000
Restricted shares issued, net of shares withheld for taxes		$ 0.0	(4.8)						(4.8)
Stock-based compensation expense	164.3						164.3
Restricted stock units issued as dividend equivalents							0.2			(0.2)
Common shares repurchased (in shares)				(10,763,000)
Common shares repurchased	(1,170.6)			$ (2.1)			(242.5)			(926.0)
Ending balance (in shares) at Sep. 30, 2020				226,375,000
Balances at end of period at Sep. 30, 2020	7,128.5			$ 45.3			654.6			6,471.3	(42.7)
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	4.4
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(13.9)
Net subscriptions into consolidated T. Rowe Price investment products	307.8
Net deconsolidations of T. Rowe Price investment products	(106.9)
Ending balances attributable to redeemable non-controlling interests at Sep. 30, 2020	1,340.2
Beginning balance (in shares) at Jun. 30, 2020				226,990,000
Balances at beginning of period at Jun. 30, 2020	6,750.7			$ 45.4			654.6			6,102.9	(52.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	643.2									643.2
Other comprehensive income (loss), net of tax	9.5										9.5
Dividends declared	(210.2)									(210.2)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				492,000
Shares issued upon option exercises	26.0			$ 0.1			25.9
Restricted shares issued, net of shares withheld for taxes (in shares)					0
Net shares issued upon vesting of restricted stock units (in shares)						17,000
Net shares issued upon vesting of restricted stock units			$ (1.6)						$ (1.6)
Stock-based compensation expense	52.8						52.8
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(1,124,000)
Common shares repurchased	(141.9)			$ (0.2)			(77.2)			(64.5)
Ending balance (in shares) at Sep. 30, 2020				226,375,000
Balances at end of period at Sep. 30, 2020	7,128.5			$ 45.3			$ 654.6			$ 6,471.3	$ (42.7)
Beginning balances attributable to redeemable non-controlling interests at Jun. 30, 2020	1,090.1
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	55.4
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(20.8)
Net subscriptions into consolidated T. Rowe Price investment products	217.9
Net deconsolidations of T. Rowe Price investment products	(44.0)
Ending balances attributable to redeemable non-controlling interests at Sep. 30, 2020	$ 1,340.2

[1] Accumulated other comprehensive income.