CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Statement of Cash Flows) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 787.7	$ 578.7
Net cash provided by (used in) investing activities	27.6	(33.8)
Net cash used in financing activities	(992.3)	(306.0)
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(1.2)	(0.7)
Net change in cash and cash equivalents during period	(178.2)	238.2
Cash and cash equivalents at beginning of period	1,858.3	1,495.3
Cash and cash equivalents at ending of period	1,680.1	1,733.5
Consolidation eliminations
Condensed Cash Flow Statements, Captions [Line Items]
Net cash used in financing activities	42.8	37.8
Consolidated T. Rowe Price investment products
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents at beginning of period	76.5	70.1
Cash and cash equivalents at ending of period	117.7	76.1
Consolidated T. Rowe Price investment products | Reportable entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(75.7)	(93.7)
Net cash provided by (used in) investing activities	(0.8)	(3.4)
Net cash used in financing activities	118.9	103.8
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(1.2)	(0.7)
Net change in cash and cash equivalents during period	41.2	6.0
Cash and cash equivalents at beginning of period	76.5	70.1
Cash and cash equivalents at ending of period	117.7	76.1
Voting interest entities | Reportable entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	11.3	(28.7)
Net cash provided by (used in) investing activities	(0.8)	(5.1)
Net cash used in financing activities	2.7	31.6
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	0.0	0.0
Net change in cash and cash equivalents during period	13.2	(2.2)
Cash and cash equivalents at beginning of period	9.9	18.5
Cash and cash equivalents at ending of period	23.1	16.3
Variable interest entities | Reportable entities
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(87.0)	(65.0)
Net cash provided by (used in) investing activities	0.0	1.7
Net cash used in financing activities	116.2	72.2
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(1.2)	(0.7)
Net change in cash and cash equivalents during period	28.0	8.2
Cash and cash equivalents at beginning of period	66.6	51.6
Cash and cash equivalents at ending of period	$ 94.6	$ 59.8