Stock Transactions and Unit Redemptions - Changes in Shares of Class A Common Stock Outstanding Table Footnote (Detail) - shares shares in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Limited Partnership
Class of Stock [Line Items]
Number of units redeemed and cancelled for exchange (in shares)	29.7	9.2
Class A Common Stock
Class of Stock [Line Items]
Common stock, shares issued (in shares)	27.5	9.5

The number of shares issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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