STOCKHOLDERS' EQUITY: Future expense, by award type (Details) $ in Millions	Dec. 31, 2019 USD ($)
Share-based compensation
Future expense for performance stock option units	$ 180.5
2020
Share-based compensation
Future expense for performance stock option units	23.9
2021
Share-based compensation
Future expense for performance stock option units	79.9
2022
Share-based compensation
Future expense for performance stock option units	47.8
2023
Share-based compensation
Future expense for performance stock option units	25.2
2024
Share-based compensation
Future expense for performance stock option units	3.7
Stock options
Share-based compensation
Share-based compensation not yet recognized	4.6
Stock options | 2020
Share-based compensation
Share-based compensation not yet recognized	0.9
Stock options | 2021
Share-based compensation
Share-based compensation not yet recognized	2.3
Stock options | 2022
Share-based compensation
Share-based compensation not yet recognized	1.1
Stock options | 2023
Share-based compensation
Share-based compensation not yet recognized	0.3
Stock options | 2024
Share-based compensation
Share-based compensation not yet recognized	0.0
Restricted stock units
Share-based compensation
Future share-based compensation expense expected	129.3
Restricted stock units | 2020
Share-based compensation
Future share-based compensation expense expected	14.4
Restricted stock units | 2021
Share-based compensation
Future share-based compensation expense expected	49.9
Restricted stock units | 2022
Share-based compensation
Future share-based compensation expense expected	38.5
Restricted stock units | 2023
Share-based compensation
Future share-based compensation expense expected	22.8
Restricted stock units | 2024
Share-based compensation
Future share-based compensation expense expected	3.7
Consideration Holdback | Data Plus Math Corporation
Share-based compensation
Future share-based compensation expense expected	20.7
Consideration Holdback | Data Plus Math Corporation | 2020
Share-based compensation
Future share-based compensation expense expected	2.1
Consideration Holdback | Data Plus Math Corporation | 2021
Share-based compensation
Future share-based compensation expense expected	8.3
Consideration Holdback | Data Plus Math Corporation | 2022
Share-based compensation
Future share-based compensation expense expected	8.2
Consideration Holdback | Data Plus Math Corporation | 2023
Share-based compensation
Future share-based compensation expense expected	2.1
Consideration Holdback | Data Plus Math Corporation | 2024
Share-based compensation
Future share-based compensation expense expected	0.0
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC
Share-based compensation
Future share-based compensation expense expected	25.9
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC | 2020
Share-based compensation
Future share-based compensation expense expected	6.5
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC | 2021
Share-based compensation
Future share-based compensation expense expected	19.4
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC | 2022
Share-based compensation
Future share-based compensation expense expected	0.0
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC | 2023
Share-based compensation
Future share-based compensation expense expected	0.0
Pacific Data Partners, LLC Agreement Plan | Pacific Data Partners LLC | 2024
Share-based compensation
Future share-based compensation expense expected	$ 0.0