CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Statement of Cash Flows) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	$ 1,500.7	$ 1,486.4
Net cash used in investing activities	(76.7)	(830.4)
Net cash used in financing activities	(623.0)	(463.1)
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(2.2)	(2.4)
Net change in cash and cash equivalents during period	798.8	190.5
Cash and cash equivalents at beginning of period	1,495.3	2,005.8
Cash and cash equivalents at ending of period	2,294.1	2,196.3
Consolidation eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash used in financing activities	157.7	111.7
Consolidated T. Rowe Price investment products [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents at beginning of period	70.1	103.1
Cash and cash equivalents at ending of period	80.9	105.7
Consolidated T. Rowe Price investment products [Member] \| Reportable entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(523.5)	(570.4)
Net cash used in investing activities	(8.3)	(22.5)
Net cash used in financing activities	544.8	597.9
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(2.2)	(2.4)
Net change in cash and cash equivalents during period	10.8	2.6
Cash and cash equivalents at beginning of period	70.1	103.1
Cash and cash equivalents at ending of period	80.9	105.7
Voting interest entities [Member] \| Reportable entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(15.1)	(40.7)
Net cash used in investing activities	(7.4)	(0.8)
Net cash used in financing activities	15.5	52.3
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	(7.0)	10.8
Cash and cash equivalents at beginning of period	18.5	7.1
Cash and cash equivalents at ending of period	11.5	17.9
Variable interest entities [Member] \| Reportable entities [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash provided by operating activities	(508.4)	(529.7)
Net cash used in investing activities	(0.9)	(21.7)
Net cash used in financing activities	529.3	545.6
Effect of exchange rate changes on cash and cash equivalents of consolidated T. Rowe Price investment products	(2.2)	(2.4)
Net change in cash and cash equivalents during period	17.8	(8.2)
Cash and cash equivalents at beginning of period	51.6	96.0
Cash and cash equivalents at ending of period	$ 69.4	$ 87.8

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