Derivative Instruments (Schedule of Information About Interest Rate Swaps) Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Derivative [Line Items]
Notional Amount	$ 273,425,000	$ 32,600,000
Swap [Member]
Derivative [Line Items]
Notional Amount	169,425,000	32,600,000
Weighted Average Pay Rate	1.88%	1.51%
Weighted Average Receive Rate	0.28%	0.31%
Weighted Average Years to Maturity	8 years 9 months 18 days	5 years 3 months 18 days
Cash pledged as collateral against interest rate swaps which the Company has a right to reclaim	7,582,948	2,432,846
Swap [Member] | Derivative - Maturity Date One [Member]
Derivative [Line Items]
Maturity	Dec. 31, 2016	Dec. 31, 2016
Notional Amount	12,102,000	12,102,000
Weighted Average Pay Rate	1.21%	1.21%
Weighted Average Receive Rate	0.28%	0.31%
Weighted Average Years to Maturity	3 years 6 months	3 years 8 months 12 days
Swap [Member] | Derivative - Maturity Date Two [Member]
Derivative [Line Items]
Maturity	Dec. 31, 2017	Dec. 31, 2017
Notional Amount	11,050,000	11,050,000
Weighted Average Pay Rate	1.28%	1.28%
Weighted Average Receive Rate	0.28%	0.31%
Weighted Average Years to Maturity	4 years 0 months	4 years 3 months 18 days
Swap [Member] | Derivative - Maturity Date Three [Member]
Derivative [Line Items]
Maturity	Dec. 31, 2018
Notional Amount	5,000,000
Weighted Average Pay Rate	0.88%
Weighted Average Receive Rate	0.28%
Weighted Average Years to Maturity	4 years 9 months 18 days
Swap [Member] | Derivative - Maturity Date Four [Member]
Derivative [Line Items]
Maturity	Dec. 31, 2021	Dec. 31, 2021
Notional Amount	9,448,000	9,448,000
Weighted Average Pay Rate	2.16%	2.16%
Weighted Average Receive Rate	0.28%	0.31%
Weighted Average Years to Maturity	8 years 6 months	8 years 8 months 12 days
Swap [Member] | Derivative - Maturity Date Five [Member]
Derivative [Line Items]
Maturity	Dec. 31, 2023
Notional Amount	$ 131,825,000
Weighted Average Pay Rate	2.01%
Weighted Average Receive Rate	0.28%
Weighted Average Years to Maturity	9 years 10 months 24 days