Debt - Summary of Outstanding Debt (Details) - USD ($) $ in Thousands			9 Months Ended
	Jul. 17, 2017	Jan. 19, 2017	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate			3.60%
Notes and mortgages payable			$ 3,583,100	$ 3,408,179
Credit Facility				230,000
Less: deferred financing costs			(44,029)	(43,281)
Total notes and mortgages payable, net			$ 3,539,071	3,364,898
Credit Facility With Variable Rate [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date of debt			2018-11
Credit Facility				230,000
Credit Facility With Variable Rate [Member] | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Fixed/Variable Rate			1.25%
50 Beale Street [Member]
Debt Instrument [Line Items]
Maturity date of debt	2021-10
50 Beale Street [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2021-10
Notes and mortgages payable, Interest Rate			3.65%
Notes and mortgages payable			$ 228,000
1633 Broadway [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate			3.52%
Notes and mortgages payable			$ 1,030,100	1,013,544
1633 Broadway [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2022-12
Notes and mortgages payable, Interest Rate			3.54%
Notes and mortgages payable			$ 1,000,000	1,000,000
1633 Broadway [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2022-12
Notes and mortgages payable, Interest Rate			3.00%
Notes and mortgages payable			$ 30,100	13,544
1633 Broadway [Member] | Mortgages and Notes Payable with Variable Rate [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Fixed/Variable Rate			1.75%
One Market Plaza [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate			4.03%
Notes and mortgages payable			$ 975,000	872,960
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%
Notes and mortgages payable			$ 975,000	860,546
One Market Plaza [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				12,414
1301 Avenue of Americas [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate			3.05%
Notes and mortgages payable			$ 850,000	850,000
1301 Avenue of Americas [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2021-11
Notes and mortgages payable, Interest Rate			3.05%
Notes and mortgages payable			$ 500,000	500,000
1301 Avenue of Americas [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2021-11
Notes and mortgages payable, Interest Rate			3.05%
Notes and mortgages payable			$ 350,000	350,000
1301 Avenue of Americas [Member] | Mortgages and Notes Payable with Variable Rate [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Fixed/Variable Rate			1.80%
31 West 52nd Street [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt			2026-05
Notes and mortgages payable, Interest Rate			3.80%
Notes and mortgages payable			$ 500,000	500,000
1899 Pennsylvania Avenue [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				87,675
Liberty Place [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				$ 84,000