CONSOLIDATED T. ROWE PRICE INVESTMENT PRODUCTS. (Fair Value Measurements) (Details) - Fair value, measurements, recurring - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 1,164.9	$ 1,355.6
Total	2,740.6	3,309.7
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0.0	0.0
Total	12.4	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	22.5	9.1
Total	175.7	174.6
Liabilities	(2.3)	(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
Total	1,685.4	2,008.0
Liabilities	(31.9)	(11.2)
Consolidated T. Rowe Price investment products | Equity securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	149.9	162.8
Consolidated T. Rowe Price investment products | Equity securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	548.3	724.5
Consolidated T. Rowe Price investment products | Fixed income securities | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0.0	0.0
Consolidated T. Rowe Price investment products | Fixed income securities | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	1,097.9	1,248.6
Consolidated T. Rowe Price investment products | Other investments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	3.3	2.7
Consolidated T. Rowe Price investment products | Other investments | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 39.2	$ 33.8