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Stockholders' Equity - Share Activity by Class of Stock (Details) - shares	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	76,942,872
Restricted share award net share settlement (in shares)	(74,006)
Ending balance (in shares)	77,814,721
Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	54,071,188
Restricted share award net share settlement (in shares)	(74,006)
Ending balance (in shares)	56,145,554
Class B Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	8,645,249
Restricted share award net share settlement (in shares)	0
Ending balance (in shares)	7,912,056
Class C Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	14,226,435
Restricted share award net share settlement (in shares)	0
Ending balance (in shares)	13,757,111
Holdings GP Units
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	54,071,188
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Holdings Common Unit Exchanges (in shares)	0
Common Stock | Class B Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Holdings Common Unit Exchanges (in shares)	(733,193)
Common Stock | Class C Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Holdings Common Unit Exchanges (in shares)	(469,324)
Common Stock | Holdings GP Units
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Holdings Common Unit Exchanges (in shares)	(1,202,517)
Restricted Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)	959,000
Restricted Stock | Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)	959,000
Restricted Stock | Class B Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)	0
Restricted Stock | Class C Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued (in shares)	0
Restricted Stock Units RSUs
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units outstanding (in shares)	297,891	246,581
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee/Partner Terminations (in shares)	(13,145)
Common Stock | Class A Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee/Partner Terminations (in shares)	(13,145)
Common Stock | Class B Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee/Partner Terminations (in shares)	0
Common Stock | Class C Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee/Partner Terminations (in shares)	0

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Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation.

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Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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For net-share settlement of share-based awards when the employer settles employees' income tax withholding obligations, this element represents the number of shares the employees use to repay the employer.

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