Deferred Tax Assets and Income Taxes (Details) (USD $)	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2009
Deferred tax assets
Reserves for loan losses	$ 8,605,000			$ 8,605,000		$ 14,348,000
Forgone interest on non-accrual loans	932,000			932,000		884,000
Fixed assets	555,000			555,000		405,000
Accruals	927,000			927,000		792,000
Alternative minimum tax credit	3,940,000			3,940,000		2,153,000
Deferred income	2,062,000			2,062,000		1,838,000
Deferred compensation	1,572,000			1,572,000		1,477,000
Net operating loss carryforward	189,000			189,000		907,000
Investment securities valuation	1,089,000			1,089,000
Other than temporary impairment						45,000
Realized built-in loss subject to 382	2,473,000			2,473,000		3,234,000
Charitable contribution	61,000			61,000		61,000
State deferred tax	663,000			663,000		59,000
Total deferred tax assets	23,068,000			23,068,000		26,203,000
Deferred tax liabilities
Fair value adjustment for purchased assets	399,000			399,000		455,000
Investment securities valuation						2,745,000
Deferred costs, prepaids and FHLB advances	909,000			909,000		1,070,000
Total deferred tax liabilities	1,308,000			1,308,000		4,270,000
Net deferred tax assets	21,760,000			21,760,000		21,933,000
Cumulative loss position period							3 years	3 years
Change in deferred tax asset valuation allowance		(700,000)	(1,500,000)		(1,500,000)	(5,600,000)	7,100,000
Determination of the valuation allowance, cumulative pre-tax losses period							3 years
Determination of the valuation allowance, expected deferred tax assets realization period							5 years
Current:
Federal	1,859,000	940,000		(189,000)	1,553,000
State	489,000	449,000		278,000	472,000
Total current (benefit) / expense	2,348,000	1,389,000		89,000	2,025,000
Deferred:
Federal	(630,000)	(605,000)		3,147,000	(920,000)
State	(13,000)	(278,000)		860,000	(173,000)
Total deferred expense / (benefit)	(643,000)	(883,000)		4,007,000	(1,093,000)
Deferred Tax Valuation Allowance:
Federal		(518,000)			(1,110,000)
State		(182,000)			(390,000)
Total deferred tax valuation allowance change		(700,000)			(1,500,000)
Total income tax expense / (benefit)	1,705,000	(194,000)		4,096,000	(568,000)
Reconciliation of the statutory federal income tax expense / (benefit) to the Company's effective income tax expense / (benefit)
Tax expense at federal statutory tax rate	1,547,000	598,000		3,689,000	1,020,000
State income taxes, net of federal income tax benefit	310,000	111,000		740,000	194,000
Change in deferred tax asset valuation allowance		(700,000)			(1,500,000)
Bank owned life insurance	(32,000)	(31,000)		(77,000)	(53,000)
Tax exempt income, net of interest expense	(94,000)	(116,000)		(226,000)	(198,000)
Other, net	(26,000)	(56,000)		(30,000)	(31,000)
Total income tax expense / (benefit)	$ 1,705,000	$ (194,000)		$ 4,096,000	$ (568,000)
Reconciliation of the statutory federal income tax expense / (benefit) rate to the Company's effective income tax expense / (benefit) rate
Tax expense at federal statutory tax rate (as a percent)	35.00%	35.00%		35.00%	35.00%
State income taxes, net of federal income tax benefit (as a percent)	7.00%	6.50%		7.00%	6.70%
Change in deferred tax asset valuation allowance (as a percent)	0.00%	(41.00%)		0.00%	(51.50%)
Bank owned life insurance (as a percent)	(0.70%)	(1.80%)		(0.70%)	(1.80%)
Tax exempt income, net of interest expense (as a percent)	(2.10%)	(6.80%)		(2.10%)	(6.80%)
Other, net (as a percent)	(0.60%)	(3.30%)		(0.30%)	(1.10%)
Total income tax expense / (benefit) (as a percent)	38.60%	(11.40%)		38.90%	(19.50%)