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Stockholders' Equity Share Activity by Class (Details) - shares | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Class of Stock [Line Items] |  |  |  |
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation | (82,729) | (77,442) | (48,646) |
Outstanding | 77,801,854 | 76,942,872 | 75,569,845 | 74,354,869
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number | 297,891 | 246,581 | 178,401 |
Class A Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues |  | (644,424) |  |
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation | (82,729) | (77,442) | (48,646) |
Outstanding | 56,429,825 | 54,071,188 | 50,463,126 | 42,149,436
Class B Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues |  | (644,424) | (2,104,517) |
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation | 0 | 0 | 0 |
Outstanding | 7,803,364 | 8,645,249 | 11,922,192 | 15,142,049
Class C Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues |  | 0 | (3,522,000) |
Share-based Payment Arrangement, Shares Withheld for Tax Withholding Obligation | 0 | 0 | 0 |
Outstanding | 13,568,665 | 14,226,435 | 13,184,527 | 17,063,384
Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | (17,289) | (67,255) | (3,628) |
Common Stock | Class A Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) |  | (67,255) | (3,628) |
Common Stock | Class B Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | 0 | (2,026,453) | (66,423) |
Common Stock | Class C Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues | 0 | (2,026,453) | (66,423) |
Common Stock | Class A Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) |  | (1,590,611) | (1,472,197) |
Common Stock | Class B Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | (841,885) | (606,066) | (1,048,917) |
Common Stock | Class C Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | (657,770) | (984,545) | (423,280) |
Unvested restricted share-based awards |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues | (959,000) | (1,517,724) | (1,267,250) |
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | 5,005,422 | 4,678,457 | 4,013,986 | 3,394,910
Unvested restricted share-based awards | Class A Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Stock Issued During Period, Shares, New Issues | (959,000) | (1,517,724) | (1,267,250) |
Unvested restricted share-based awards | Class B Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | 0 | 0 | 0 |
Unvested restricted share-based awards | Class C Common Stock |  |  |  |
Class of Stock [Line Items] |  |  |  |
Shares repurchased and retired during the period (shares) | 0 | 0 | 0 |

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