Derivatives Instruments and Hedging Activities - Summary of Outstanding Interest Rate Swaps (Details) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 16, 2015	Dec. 31, 2014
Derivative [Line Items]
Interest rate swap liabilities	$ 163,301,000		$ 194,196,000
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	2,200,000,000
Interest rate swap liabilities	144,699,000		194,196,000
Not Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$ 772,100,000
Maturity Date	2016-12
Strike Rate	4.92%
Interest rate swap liabilities	$ 40,043,000		60,191,000
Not Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Minimum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2006-12
Not Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Maximum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2008-06
Not Designated as Hedging Instrument [Member] | 900 Third Avenue [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$ 255,000,000
Strike Rate	4.15%
Interest rate swap liabilities	$ 14,495,000		19,158,000
Not Designated as Hedging Instrument [Member] | 900 Third Avenue [Member] | Minimum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2007-11
Maturity Date	2015-11
Not Designated as Hedging Instrument [Member] | 900 Third Avenue [Member] | Maximum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2012-11
Maturity Date	2017-12
Not Designated as Hedging Instrument [Member] | 31 West 52nd Street [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$ 337,500,000
Strike Rate	4.49%
Interest rate swap liabilities	$ 22,114,000		28,748,000
Not Designated as Hedging Instrument [Member] | 31 West 52nd Street [Member] | Minimum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2007-12
Maturity Date	2015-12
Not Designated as Hedging Instrument [Member] | 31 West 52nd Street [Member] | Maximum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2012-12
Maturity Date	2017-12
Not Designated as Hedging Instrument [Member] | One Market Plaza [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Notional Amount	$ 840,000,000
Maturity Date	2017-08
Strike Rate	5.02%
Interest rate swap liabilities	$ 68,047,000		$ 86,099,000
Not Designated as Hedging Instrument [Member] | One Market Plaza [Member] | Minimum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2007-08
Not Designated as Hedging Instrument [Member] | One Market Plaza [Member] | Maximum | Interest Rate Swap [Member]
Derivative [Line Items]
Effective Dates	2012-08
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Interest rate swap liabilities	$ 18,602,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Notional Amount	$ 1,000,000,000	$ 1,000,000,000
Effective Dates	2015-12
Strike Rate	1.79%
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Minimum | Interest Rate Swap [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Maturity Date	2020-12
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Maximum | Interest Rate Swap [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Maturity Date	2022-12