Debt - Additional Information (Details) ft² in Millions		9 Months Ended
	Jan. 19, 2017 USD ($) ft²	Sep. 30, 2017 ft²
Debt Instrument [Line Items]
Area of office and retail properties | ft²		12.5
Notes and mortgages payable, interest rate		3.60%
One Market Plaza [Member]
Debt Instrument [Line Items]
Mortgage refinancing extended amount | $	$ 975,000,000
Area of office and retail properties | ft²	1.6
Debt instrument term of notes	7 years
Notes and mortgages payable, interest rate		4.03%
Prepayment cost related to mortgage loan | $	$ 2,715,000
One Market Plaza [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt	2024-02	2024-02
Notes and mortgages payable, interest rate	4.03%	4.03%