Debt - Summary of Outstanding Debt (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Oct. 06, 2016	May 03, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate	4.10%
Notes and mortgages payable	$ 3,408,179,000			$ 2,941,524,000
Credit Facility	230,000,000			20,000,000
Less: deferred financing costs	(43,281,000)			(18,914,000)
Total notes and mortgages payable, net	$ 3,364,898,000			2,922,610,000
Credit Facility With Variable Rate [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date of debt	2018-11
Interest Rate	2.02%
Credit Facility	$ 230,000,000			20,000,000
Credit Facility With Variable Rate [Member] | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Fixed/Variable Rate	1.25%
1633 Broadway [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate	3.52%
Notes and mortgages payable	$ 1,013,544,000			1,013,544,000
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	$ 1,000,000,000			1,000,000,000
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	2.37%
Notes and mortgages payable	$ 13,544,000			13,544,000
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%
1301 Avenue of Americas [Member]
Debt Instrument [Line Items]
Maturity date of debt	2021-10
Notes and mortgages payable, Interest Rate	2.79%	2.77%
Notes and mortgages payable	$ 850,000,000
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	$ 500,000,000
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	2.43%
Notes and mortgages payable	$ 350,000,000
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%
900 Third Avenue [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				274,337,000
900 Third Avenue [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				162,000,000
900 Third Avenue [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				112,337,000
31 West 52nd Street [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate	3.80%
Notes and mortgages payable	$ 500,000,000			413,490,000
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%		3.80%
Notes and mortgages payable	$ 500,000,000			237,600,000
31 West 52nd Street [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				175,890,000
One Market Plaza [Member]
Debt Instrument [Line Items]
Notes and mortgages payable, Interest Rate	6.12%
Notes and mortgages payable	$ 872,960,000			857,037,000
One Market Plaza [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt	2019-12
Notes and mortgages payable, Interest Rate	6.13%
Notes and mortgages payable	$ 860,546,000			857,037,000
One Market Plaza [Member] | Mortgages and Notes Payable with Variable Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt	2019-12
Notes and mortgages payable, Interest Rate	4.94%
Notes and mortgages payable	$ 12,414,000
One Market Plaza [Member] | Mortgages and Notes Payable with Variable Rate [Member] | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Fixed/Variable Rate	4.20%
Waterview [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Notes and mortgages payable				210,000,000
1899 Pennsylvania Avenue [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt	2020-11
Notes and mortgages payable, Interest Rate	4.88%
Notes and mortgages payable	$ 87,675,000			89,116,000
Liberty Place [Member] | Mortgages and Notes Payable with Fixed Rate [Member]
Debt Instrument [Line Items]
Maturity date of debt	2018-06
Notes and mortgages payable, Interest Rate	4.50%
Notes and mortgages payable	$ 84,000,000			$ 84,000,000