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COMMON STOCK AND CHANGES IN CAPITALIZATION (Details) - USD ($) |  | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Feb. 17, 2017 | Sep. 30, 2018 | Sep. 30, 2018 | May 31, 2018 | Jan. 31, 2018
Class of Stock [Line Items] |  |  |  |  |
Stock repurchase program, amount authorized to acquire |  |  |  |  | $ 100,000,000
Amount of shares repurchased |  | $ 5,000,000 | $ 109,997,000 |  |
Vitruvian acquisition |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Total initial purchase price | $ 1,850,000,000 |  |  |  |
Payments to acquire businesses | $ 1,354,093,000 |  |  |  |
Equity interest issued or issuable, number of shares (in shares) | 23,900,000 |  |  |  |
Vitruvian acquisition | Indemnity escrow |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Equity interest issued or issuable, number of shares (in shares) | 5,200,000 |  |  |  |
Common Stock |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Shares repurchased (in shares) |  | 400,000 | 10,505,469 |  |
Amount of shares repurchased |  |  | $ 105,000 |  |
Minimum |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Stock repurchase program, amount authorized to acquire |  |  |  | $ 100,000,000 |
Maximum |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |
Stock repurchase program, amount authorized to acquire |  |  |  | $ 200,000,000 |

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