CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Operating Results) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Condensed Income Statements, Captions [Line Items]
Operating expenses reflected in net operating income	$ (866.9)	$ (767.6)	$ (2,484.0)	$ (2,342.5)
Income before income taxes	920.5	702.1	2,096.2	2,177.0
Net income (loss) attributable to redeemable non-controlling interests	55.4	(0.8)	4.4	69.0
Consolidation eliminations
Condensed Income Statements, Captions [Line Items]
Operating expenses reflected in net operating income	(2.7)	(2.6)	(7.3)	(6.3)
Consolidated T. Rowe Price investment products
Condensed Income Statements, Captions [Line Items]
Income before income taxes	96.8	7.9	1.6	165.7
Net income (loss) attributable to T. Rowe Price Group	41.4	8.7	(2.8)	96.7
Net income (loss) attributable to redeemable non-controlling interests	55.4	(0.8)	4.4	69.0
Consolidated T. Rowe Price investment products | Reportable entities
Condensed Income Statements, Captions [Line Items]
Operating expenses reflected in net operating income	(4.4)	(3.7)	(11.7)	(10.6)
Net investment income (loss) reflected in non-operating income (loss)	101.2	11.6	13.3	176.3
Income before income taxes	96.8	7.9	1.6	165.7
Voting interest entities
Condensed Income Statements, Captions [Line Items]
Income before income taxes	12.4	0.9	(6.9)	19.3
Net income (loss) attributable to T. Rowe Price Group	7.0	0.7	(2.7)	14.6
Net income (loss) attributable to redeemable non-controlling interests	5.4	0.2	(4.2)	4.7
Voting interest entities | Reportable entities
Condensed Income Statements, Captions [Line Items]
Operating expenses reflected in net operating income	(0.7)	(0.6)	(1.2)	(1.6)
Net investment income (loss) reflected in non-operating income (loss)	13.1	1.5	(5.7)	20.9
Income before income taxes	12.4	0.9	(6.9)	19.3
Variable interest entities
Condensed Income Statements, Captions [Line Items]
Income before income taxes	84.4	7.0	8.5	146.4
Net income (loss) attributable to T. Rowe Price Group	34.4	8.0	(0.1)	82.1
Net income (loss) attributable to redeemable non-controlling interests	50.0	(1.0)	8.6	64.3
Variable interest entities | Reportable entities
Condensed Income Statements, Captions [Line Items]
Operating expenses reflected in net operating income	(3.7)	(3.1)	(10.5)	(9.0)
Net investment income (loss) reflected in non-operating income (loss)	88.1	10.1	19.0	155.4
Income before income taxes	$ 84.4	$ 7.0	$ 8.5	$ 146.4