Derivative Financial Instruments - Fair Value of Derivatives (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Current Fiscal Year End Date	--12-31
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 172,632
Long-term Debt, Maturities, Repayments of Principal in Year Two	418,182
Long-term Debt, Maturities, Repayments of Principal in Year Three	102,148
Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	395,000
Derivative @ 2.867% 95M [Member] [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Apr. 15, 2014
Derivative @ 2.087% 75K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Apr. 15, 2014
Derivative, Maturity Date	Apr. 15, 2024
Derivative, Early Termination Date	Oct. 15, 2014
Derivative, Notional Amount	75,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.087%
Derivative Asset, Fair Value, Gross Asset	7,476	1,022
Derivative @ 2.088% 50K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Apr. 15, 2014
Derivative, Maturity Date	Apr. 15, 2024
Derivative, Early Termination Date	Oct. 15, 2014
Derivative, Notional Amount	50,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.088%
Derivative Asset, Fair Value, Gross Asset	4,978	672
Derivative @ 2.864% 60K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Maturity Date	Apr. 15, 2024
Derivative, Early Termination Date	Oct. 15, 2014
Derivative, Notional Amount	60,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.864%
Derivative Asset, Fair Value, Gross Asset	1,821	0
Derivative @ 2.873% 35K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Apr. 15, 2014
Derivative, Maturity Date	Apr. 15, 2024
Derivative, Early Termination Date	Oct. 15, 2014
Derivative, Notional Amount	35,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.8725%
Derivative Asset, Fair Value, Gross Asset	1,036	0
Derivative @ 2.479% 75K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Aug. 01, 2015
Derivative, Maturity Date	Aug. 01, 2025
Derivative, Early Termination Date	Feb. 01, 2016
Derivative, Notional Amount	75,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.479%
Derivative Asset, Fair Value, Gross Asset	8,516	1,131
Derivative A @ 2.479% 50K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Aug. 01, 2015
Derivative, Maturity Date	Aug. 01, 2025
Derivative, Early Termination Date	Feb. 01, 2016
Derivative, Notional Amount	50,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.479%
Derivative Asset, Fair Value, Gross Asset	5,670	729
Derivative B @ 2.479% 50K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Aug. 01, 2015
Derivative, Maturity Date	Aug. 01, 2025
Derivative, Early Termination Date	Feb. 01, 2016
Derivative, Notional Amount	50,000
Derivative, Description of Variable Rate Basis	3 Month LIBOR
Derivative, Fixed Interest Rate	2.479%
Derivative Asset, Fair Value, Gross Asset	5,658	753
Derivative @ 2.196% 28.1K [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Oct. 16, 2013
Derivative, Maturity Date	Oct. 16, 2020
Derivative, Notional Amount	28,100
Derivative, Description of Variable Rate Basis	1 Month LIBOR
Derivative, Fixed Interest Rate	2.196%
Derivative Asset, Fair Value, Gross Asset	82	0
.76% Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative, Inception Date	Oct. 01, 2011
Derivative, Maturity Date	Sep. 01, 2014
Derivative, Notional Amount	9,000
Derivative, Description of Variable Rate Basis	1 Month LIBOR
Derivative, Fixed Interest Rate	0.76%
Derivative Liability, Fair Value, Gross Liability	(34)	(76)
Unsecured Maturities [Member]
Derivatives, Fair Value [Line Items]
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	150,000
Long-term Debt, Maturities, Repayments of Principal in Year Two	350,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	$ 75,000