Debt - Summary of Outstanding Debt (Parenthetical) (Details) - USD ($) $ in Billions	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Revolving Credit Facility [Member] | Credit Facility With Variable Rate [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 1.0	$ 1.0
1633 Broadway [Member]
Debt Instrument [Line Items]
Ownership percentage of Property	90.00%	90.00%
One Market Plaza [Member]
Debt Instrument [Line Items]
Ownership percentage of Property	49.00%	49.00%
300 Mission Street [Member]
Debt Instrument [Line Items]
Ownership percentage of Property	31.10%	31.10%
1301 Avenue of the Americas [Member] | London Interbank Offered Rate (LIBOR) [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Capped interest rate	2.00%	2.00%