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	1,040.1									1,040.1
Other comprehensive income (loss), net of tax	3.5										3.5
Dividends declared	(367.2)									(367.2)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				1,495,000
Shares issued upon option exercises	82.8			$ 0.3			82.5
Restricted shares issued, net of shares withheld for taxes (in shares)					7,000	33,000
Restricted shares issued, net of shares withheld for taxes		$ (0.1)	$ (1.4)					$ (0.1)	$ (1.4)
Forfeiture of restricted awards (in shares)				(7,000)
Stock-based compensation expense	90.7						90.7
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(4,079,000)
Common shares repurchased	(393.6)			$ (0.8)			(171.8)			(221.0)
Ending balance (in shares) at Jun. 30, 2019				235,518,000
Balances at end of period at Jun. 30, 2019	6,579.1			$ 47.1			654.6			5,915.9	(38.5)
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	69.8
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	0.3
Net subscriptions into consolidated T. Rowe Price investment products	211.6
Net deconsolidations of T. Rowe Price investment products	(9.1)
Ending balances attributable to redeemable non-controlling interests at Jun. 30, 2019	1,012.3
Beginning balance (in shares) at Mar. 31, 2019				236,432,000
Balances at beginning of period at Mar. 31, 2019	6,311.0			$ 47.3			654.5			5,650.8	(41.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	527.5									527.5
Other comprehensive income (loss), net of tax	3.1										3.1
Dividends declared	(183.4)									(183.4)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				665,000
Shares issued upon option exercises	37.8			$ 0.1			37.7
Restricted shares issued, net of shares withheld for taxes (in shares)					7,000
Restricted shares issued, net of shares withheld for taxes		(0.1)						$ (0.1)
Net shares issued upon vesting of restricted stock units (in shares)						19,000
Net shares issued upon vesting of restricted stock units			(0.2)						(0.2)
Forfeiture of restricted awards (in shares)				(2,000)
Stock-based compensation expense	47.2						47.2
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(1,603,000)
Common shares repurchased	(163.8)			$ (0.3)			(84.6)			(78.9)
Ending balance (in shares) at Jun. 30, 2019				235,518,000
Balances at end of period at Jun. 30, 2019	6,579.1			$ 47.1			654.6			5,915.9	(38.5)
Beginning balances attributable to redeemable non-controlling interests at Mar. 31, 2019	886.7
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	28.4
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(1.0)
Net subscriptions into consolidated T. Rowe Price investment products	125.7
Net deconsolidations of T. Rowe Price investment products	(29.5)
Ending balances attributable to redeemable non-controlling interests at Jun. 30, 2019	1,012.3
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	946.1									946.1
Other comprehensive income (loss), net of tax	(9.2)										(9.2)
Dividends declared	$ (425.1)									(425.1)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)	1,944,942			1,364,000
Shares issued upon option exercises	$ 57.2			$ 0.3			56.9
Restricted shares issued, net of shares withheld for taxes (in shares)					8,000	43,000
Restricted shares issued, net of shares withheld for taxes		$ 0.0	(3.3)						(3.3)
Stock-based compensation expense	111.6						111.6
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(9,639,000)
Common shares repurchased	(1,028.7)			$ (1.9)			(165.3)			(861.5)
Ending balance (in shares) at Jun. 30, 2020				226,990,000
Balances at end of period at Jun. 30, 2020	6,750.7			$ 45.4			654.6			6,102.9	(52.2)
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	(51.0)
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	6.9
Net subscriptions into consolidated T. Rowe Price investment products	89.9
Net deconsolidations of T. Rowe Price investment products	(62.9)
Ending balances attributable to redeemable non-controlling interests at Jun. 30, 2020	1,090.1
Beginning balance (in shares) at Mar. 31, 2020				227,985,000
Balances at beginning of period at Mar. 31, 2020	6,434.0			$ 45.6			654.6			5,782.9	(49.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	603.0									603.0
Other comprehensive income (loss), net of tax	(3.1)										(3.1)
Dividends declared	(210.3)									(210.3)
Common stock-based compensation plans activity
Shares issued upon option exercises (in shares)				296,000
Shares issued upon option exercises	15.9			$ 0.1			15.8
Restricted shares issued, net of shares withheld for taxes (in shares)					8,000
Net shares issued upon vesting of restricted stock units (in shares)						6,000
Net shares issued upon vesting of restricted stock units			$ (0.3)						$ (0.3)
Stock-based compensation expense	53.3						53.3
Restricted stock units issued as dividend equivalents							0.1			(0.1)
Common shares repurchased (in shares)				(1,305,000)
Common shares repurchased	(141.8)			$ (0.3)			(68.9)			(72.6)
Ending balance (in shares) at Jun. 30, 2020				226,990,000
Balances at end of period at Jun. 30, 2020	6,750.7			$ 45.4			$ 654.6			$ 6,102.9	$ (52.2)
Beginning balances attributable to redeemable non-controlling interests at Mar. 31, 2020	971.0
Increase (Decrease) in Temporary Equity [Roll Forward]
Net income (loss) attributable to redeemable non-controlling interests	125.5
Other comprehensive income (loss), net of tax, attributable to redeemable non-controlling interests	(10.3)
Net subscriptions into consolidated T. Rowe Price investment products	26.1
Net deconsolidations of T. Rowe Price investment products	(42.8)
Ending balances attributable to redeemable non-controlling interests at Jun. 30, 2020	$ 1,090.1

[1] Accumulated other comprehensive income.