Derivative Instruments and Hedging Activities - Summary of Outstanding Interest Rate Swaps (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Interest rate swap assets	$ 730,000	$ 139,000
Interest rate swap liabilities	1,819,000	22,446,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount		$ 400,000,000
Effective Dates, Liabilities		2015-12
Maturity Date, Liabilities		2020-12
Strike Rate, Liabilities		1.65%
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Cash Flow Hedges [Member] | Other Assets [Member]
Derivative [Line Items]
Interest rate swap assets	730,000	$ 139,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap Two Thousand Fifteen to Two Thousand Twenty [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Notional Amount, Assets	$ 400,000,000
Effective Dates, Assets	2015-12
Maturity Date, Assets	2020-12
Strike Rate, Assets	1.65%
Interest rate swap assets	$ 730,000
Interest rate swap liabilities		12,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap Two Thousand Twenty to Two Thousand Twenty One [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Notional Amount, Assets	$ 400,000,000
Effective Dates, Assets	2020-12
Maturity Date, Assets	2021-12
Strike Rate, Assets	2.35%
Interest rate swap assets		139,000
Aggregate notional amount		$ 400,000,000
Effective Dates, Liabilities		2020-12
Maturity Date, Liabilities		2021-12
Strike Rate, Liabilities		2.35%
Interest rate swap liabilities	$ 659,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap Two Thousand Fifteen to Two Thousand Twenty Two [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount		$ 300,000,000
Effective Dates, Liabilities		2015-12
Maturity Date, Liabilities		2022-12
Strike Rate, Liabilities		1.95%
Interest rate swap liabilities	993,000	$ 828,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap Two Thousand Fifteen to Two Thousand Twenty One [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount		$ 300,000,000
Effective Dates, Liabilities		2015-12
Maturity Date, Liabilities		2021-12
Strike Rate, Liabilities		1.82%
Interest rate swap liabilities	167,000	$ 379,000
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap September Two Thousand Fifteen [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount		$ 300,000,000
Effective Dates, Liabilities		2015-12
Maturity Date, Liabilities		2022-12
Strike Rate, Liabilities		1.95%
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap November Two Thousand Fifteen [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount		$ 300,000,000
Effective Dates, Liabilities		2015-12
Maturity Date, Liabilities		2021-12
Strike Rate, Liabilities		1.82%
Designated as Hedging Instrument [Member] | 1633 Broadway [Member] | Interest Rate Swap [Member] | Cash Flow Hedges [Member]
Derivative [Line Items]
Aggregate notional amount	1,000,000,000
Interest rate swap liabilities	$ 1,819,000	$ 1,219,000