Derivatives (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jul. 14, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Jul. 13, 2016	Dec. 31, 2015
Derivative [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net		$ (9,846,000)	$ 18,376,000	$ (26,631,000)	$ 4,494,000
Amount reclassified from accumulated other comprehensive loss		(2,500,000)	(2,250,000)	(4,952,000)	(4,500,000)
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				10,000,000
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		$ (1,643,000)		$ (1,643,000)			$ (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		$ (3,746,000)		$ (3,746,000)			(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		$ (18,660,000)		$ (18,660,000)			(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		$ (18,660,000)		$ (18,660,000)			(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		$ (383,000)		$ (383,000)			0
Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value		(43,092,000)		(43,092,000)			(20,539,000)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Liability at Fair Value		$ (43,092,000)		$ (43,092,000)			$ (20,539,000)
2017 Debt issuance [Member] | Derivative [Member]
Derivative [Line Items]
Derivative, Fixed Interest Rate		3.48%		3.48%
Subsequent Event [Member]
Derivative [Line Items]
Loss on Discontinuation of Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring	$ 40,600,000
Subsequent Event [Member] | 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%