Derivatives (Details) - USD ($)		3 Months Ended		9 Months Ended
	Jul. 14, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jul. 13, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		$ 1,294,000	$ (15,768,000)	$ (25,338,000)	$ (11,274,000)
Amount reclassified from accumulated other comprehensive loss		(2,525,000)	(2,155,000)	(7,477,000)	(6,654,000)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net		(40,586,000)	$ 0	(40,586,000)	$ 0
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months				$ 10,700,000
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	$ 40,600,000
Derivative @ 1.070% 65K [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2016
Derivative, Maturity Date				Jan. 05, 2022
Derivative, Notional Amount		$ 65,000,000		$ 65,000,000
Derivative, Description of Variable Rate Basis				1 Month LIBOR
Derivative, Fixed Interest Rate		1.07%		1.07%
Interest Rate Cash Flow Hedge Asset at Fair Value		$ 53,000		$ 53,000			$ 0
Derivative @ 1.048% 200K [Member]
Derivative [Line Items]
Derivative, Inception Date				Aug. 01, 2016
Derivative, Maturity Date				Jan. 05, 2022
Derivative, Notional Amount		$ 200,000,000		$ 200,000,000
Derivative, Description of Variable Rate Basis				1 Month LIBOR
Derivative, Fixed Interest Rate		1.0477%		1.0477%
Interest Rate Cash Flow Hedge Asset at Fair Value		$ 423,000		$ 423,000			0
Assets [Member]
Derivative [Line Items]
Derivative, Notional Amount		220,000,000		$ 220,000,000
Derivative @ 2.196% 28.1M [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%
Interest Rate Cash Flow Hedge Liability at Fair Value		$ (1,373,000)		$ (1,373,000)			(898,000)
Derivative @ 3.488% 20K [Member]
Derivative [Line Items]
Derivative, Inception Date				Jun. 15, 2017
Derivative, Maturity Date				Jun. 15, 2027
Derivative, Early Termination Date				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%
Interest Rate Cash Flow Hedge Liability at Fair Value		$ 0		$ 0			(1,798,000)
Derivative @ 3.48% 100K [Member]
Derivative [Line Items]
Derivative, Inception Date				Jun. 15, 2017
Derivative, Maturity Date				Jun. 15, 2027
Derivative, Early Termination Date				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%
Interest Rate Cash Flow Hedge Liability at Fair Value		$ 0		$ 0			(8,922,000)
Swap [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months				$ 8,400,000
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				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%
Interest Rate Cash Flow Hedge Liability at Fair Value		$ 0		$ 0			(8,921,000)
Derivative @ 1.30250% 20.0M [Member]
Derivative [Line Items]
Derivative, Inception Date				Apr. 07, 2016
Derivative, Maturity Date				Apr. 01, 2023
Derivative, Notional Amount		$ 20,000,000		$ 20,000,000
Derivative, Description of Variable Rate Basis				1 Month LIBOR
Derivative, Fixed Interest Rate		1.3025%		1.3025%
Interest Rate Cash Flow Hedge Liability at Fair Value		$ (264,000)		$ (264,000)			0
Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value		476,000		476,000
Interest Rate Cash Flow Hedge Liability at Fair Value		(1,637,000)		(1,637,000)			(20,539,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value		476,000		476,000
Interest Rate Cash Flow Hedge Liability at Fair Value		(1,637,000)		(1,637,000)			(20,539,000)
Interest Rate Cash Flow Hedge Derivative at Fair Value, Net		$ 1,161,000		$ 1,161,000			$ 20,539,000
Unsecured Debt [Member]
Derivative [Line Items]
Notice of Repayment of Unsecured Debt, Subsequent to Period End Date						$ 300,000,000
Debt Instrument, Interest Rate, Stated Percentage						5.875%
2017 Debt issuance [Member] | Derivative [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		3.48%		3.48%