CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Net Assets) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 2,058.1		$ 1,781.8
Investments	2,900.0		2,939.8
Other assets	219.4		234.4
Total assets	9,477.3		9,330.4
Liabilities	1,636.5		1,107.3
Attributable to redeemable non-controlling interests	1,090.1	$ 971.0	1,121.0	$ 1,012.3	$ 886.7	$ 740.3
Consolidated T. Rowe Price investment products
Condensed Balance Sheet Statements, Captions [Line Items]
Net assets	2,106.7		2,237.7
Attributable to T. Rowe Price Group	1,016.6		1,116.7
Attributable to redeemable non-controlling interests	1,090.1		1,121.0
Consolidated T. Rowe Price investment products | Reportable entities
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	124.8		76.5
Investments	2,003.8		2,172.4
Other assets	32.9		28.0
Total assets	2,161.5		2,276.9
Liabilities	54.8		39.2
Net assets	2,106.7		2,237.7
Consolidated T. Rowe Price investment products | Reportable entities | T. Rowe Price investment products
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	45.9		40.2
Consolidated T. Rowe Price investment products | Money Market Funds | Reportable entities | T. Rowe Price investment products
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	10.5		9.1
Voting interest entities
Condensed Balance Sheet Statements, Captions [Line Items]
Net assets	142.9		289.4
Attributable to T. Rowe Price Group	111.4		199.6
Attributable to redeemable non-controlling interests	31.5		89.8
Voting interest entities | Reportable entities
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	11.4		9.9
Investments	138.0		281.1
Other assets	6.7		10.6
Total assets	156.1		301.6
Liabilities	13.2		12.2
Net assets	142.9		289.4
Variable interest entities
Condensed Balance Sheet Statements, Captions [Line Items]
Net assets	1,963.8		1,948.3
Attributable to T. Rowe Price Group	905.2		917.1
Attributable to redeemable non-controlling interests	1,058.6		1,031.2
Variable interest entities | Reportable entities
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	113.4		66.6
Investments	1,865.8		1,891.3
Other assets	26.2		17.4
Total assets	2,005.4		1,975.3
Liabilities	41.6		27.0
Net assets	$ 1,963.8		$ 1,948.3