Derivatives (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative [Line Items]
Document Period End Date				Sep. 30, 2015
Document Fiscal Year Focus				2015
Effective portion of change in fair value of derivative instruments		$ (15,768,000)	$ (3,651,000)	$ (11,274,000)	$ (28,603,000)
Amount reclassified from accumulated other comprehensive loss		(2,155,000)	(2,260,000)	(6,654,000)	(7,098,000)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net		0	$ 0	0	$ 0
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months				8,800,000
Assets [Member]
Derivative [Line Items]
Derivative, Notional Amount		220,000,000		$ 220,000,000
Derivative @ 2.196% 28.1K [Member]
Derivative [Line Items]
Derivative, Inception Date				Oct. 16, 2013
Derivative, Maturity Date				Oct. 16, 2020
Derivative, Notional Amount		$ 28,100,000		$ 28,100,000
Derivative, Description of Variable Rate Basis				1 Month LIBOR
Derivative, Fixed Interest Rate		2.196%		2.196%
Derivative Liability, Fair Value, Gross Liability	[1]	$ (1,272,000)		$ (1,272,000)		$ (764,000)
Derivative B @ 2.479% 50K [Member] [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2015
Derivative, Maturity Date				Aug. 01, 2025
Derivative, Early Termination Date	[2]			Feb. 01, 2016
Derivative, Notional Amount		$ 50,000,000		$ 50,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		2.479%		2.479%
Derivative Liability, Fair Value, Gross Liability	[1]	$ 0		$ 0		(193,000)
Derivative @ 2.479% 75K [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2015
Derivative, Maturity Date				Aug. 01, 2025
Derivative, Early Termination Date	[2]			Feb. 01, 2016
Derivative, Notional Amount		$ 75,000,000		$ 75,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		2.479%		2.479%
Derivative Liability, Fair Value, Gross Liability	[1]	$ 0		$ 0		(289,000)
Derivative A @ 2.479% 50K [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2015
Derivative, Maturity Date				Aug. 01, 2025
Derivative, Early Termination Date	[2]			Feb. 01, 2016
Derivative, Notional Amount		$ 50,000,000		$ 50,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		2.479%		2.479%
Derivative Liability, Fair Value, Gross Liability	[1]	$ 0		$ 0		(193,000)
Derivative @ 3.41% 45K [Member] [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2015
Derivative, Maturity Date				Aug. 01, 2025
Derivative, Early Termination Date	[2]			Feb. 01, 2016
Derivative, Notional Amount		$ 45,000,000		$ 45,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		3.4115%		3.4115%
Derivative Liability, Fair Value, Gross Liability	[1]	$ 0		$ 0		(3,964,000)
Derivative @ 3.488% 20K [Member]
Derivative [Line Items]
Derivative, Inception Date				Jun. 15, 2017
Derivative, Maturity Date				Jun. 15, 2027
Derivative, Early Termination Date	[2]			Dec. 15, 2017
Derivative, Notional Amount		$ 20,000,000		$ 20,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		3.4875%		3.4875%
Derivative Liability, Fair Value, Gross Liability	[1]	$ (1,933,000)		$ (1,933,000)		(1,227,000)
Derivative @ 3.48% 100K [Member]
Derivative [Line Items]
Derivative, Inception Date				Jun. 15, 2017
Derivative, Maturity Date				Jun. 15, 2027
Derivative, Early Termination Date	[2]			Dec. 15, 2017
Derivative, Notional Amount		$ 100,000,000		$ 100,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		3.48%		3.48%
Derivative Liability, Fair Value, Gross Liability	[1]	$ (9,584,000)		$ (9,584,000)		(6,080,000)
Swap [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months				$ 8,300,000
Derivative @ 3.48% 100K 2 [Member]
Derivative [Line Items]
Derivative, Inception Date				Jun. 15, 2017
Derivative, Maturity Date				Jun. 15, 2027
Derivative, Early Termination Date	[2]			Dec. 15, 2017
Derivative, Notional Amount		$ 100,000,000		$ 100,000,000
Derivative, Description of Variable Rate Basis				3 Month LIBOR
Derivative, Fixed Interest Rate		3.48%		3.48%
Derivative Liability, Fair Value, Gross Liability	[1]	$ (9,583,000)		$ (9,583,000)		(6,084,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	[1]	$ (22,372,000)		$ (22,372,000)		$ (18,794,000)
2017 Debt issuance [Member] | Derivative [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		3.48%		3.48%

[1] (2) Derivatives in an asset position are included within Other Assets in the accompanying Consolidated Balance Sheets, while those in a liability position are included within Accounts Payable and Other Liabilities.

[2] Represents the date specified in the agreement for either optional or mandatory early termination which will result in cash settlement.