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Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding (Parenthetical) (Detail) - shares shares in Millions | 3 Months Ended
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Mar. 31, 2020 | Mar. 31, 2019
Class A Common Stock [Member] |  |
Class of Stock [Line Items] |  |
Common stock, shares issued | 1.4 | 0.1
Limited Partnership [Member] |  |
Class of Stock [Line Items] |  |
Number of units redeemed and cancelled for exchange | 1.4 | 0.1

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- Definition Number of units redeemed and cancelled for exchange. + References No definition available. + Details
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Period Type: | duration

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- Details
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