CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Fair Value Measurements) (Details) - Fair value, measurements, recurring - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 1,705.1	$ 1,355.6
Other investments	0.2	0.0
Total	3,349.2	3,309.7
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Other investments	2.7	0.0
Total	12.6	9.9
Consolidated T. Rowe Price investment products | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	10.5	9.1
Equity securities	185.1	162.8
Fixed income securities	0.0	0.0
Other investments	2.5	2.7
Total	198.1	174.6
Liabilities	(0.6)	(0.4)
Consolidated T. Rowe Price investment products | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	1.1
Equity securities	668.1	724.5
Fixed income securities	1,123.1	1,248.6
Other investments	25.0	33.8
Total	1,816.2	2,008.0
Liabilities	$ (15.4)	$ (11.2)