Loans and Servicing (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loans
Total loans	$ 184,021,000	$ 181,809,000
Other items:
Net deferred loan costs	546,000	570,000
Allowance for loan losses	(1,741,000)	(1,780,000)	(1,824,000)
Total loans, net	182,826,000	180,599,000
Total loans (as a percent)	100.00%	100.00%
Residential loans:
Loans
Total loans	109,502,000	111,106,000
Other items:
Total loans (as a percent)	59.51%	61.10%
One- to four- family, residential loans
Loans
Total loans	94,689,000	95,546,000
Other items:
Allowance for loan losses	(297,000)	(378,000)	(346,000)
Total loans (as a percent)	51.46%	52.54%
Home equity loans and lines of credit
Loans
Total loans	14,813,000	15,560,000
Other items:
Allowance for loan losses	(242,000)	(254,000)	(341,000)
Total loans (as a percent)	8.05%	8.56%
Commercial loans:
Loans
Total loans	60,043,000	58,084,000
Other items:
Total loans (as a percent)	32.62%	31.95%
One-to-four family investment property
Loans
Total loans	12,164,000	11,355,000
Other items:
Allowance for loan losses	(67,000)	(62,000)	(59,000)
Total loans (as a percent)	6.61%	6.25%
Multi-family real estate
Loans
Total loans	5,451,000	5,346,000
Other items:
Allowance for loan losses	(41,000)	(40,000)	(98,000)
Total loans (as a percent)	2.96%	2.94%
Commercial real estate
Loans
Total loans	34,067,000	32,730,000
Other items:
Allowance for loan losses	(688,000)	(668,000)	(400,000)
Total loans (as a percent)	18.51%	18.00%
Commercial business
Loans
Total loans	8,361,000	8,653,000
Other items:
Allowance for loan losses	(153,000)	(159,000)	(234,000)
Total loans (as a percent)	4.54%	4.76%
Construction loans:
Loans
Total loans	14,092,000	12,205,000
Other items:
Total loans (as a percent)	7.66%	6.72%
One-to-four family, construction loans
Loans
Total loans	6,545,000	7,379,000
Other items:
Allowance for loan losses	(129,000)	(149,000)	(228,000)
Total loans (as a percent)	3.56%	4.06%
Multi-family
Loans
Total loans	3,975,000	3,665,000
Other items:
Allowance for loan losses	(37,000)	(34,000)	(98,000)
Total loans (as a percent)	2.16%	2.02%
Non-residential
Loans
Total loans	3,572,000	1,161,000
Other items:
Allowance for loan losses	(77,000)	(25,000)	(11,000)
Total loans (as a percent)	1.94%	0.64%
Consumer
Loans
Total loans	384,000	414,000
Other items:
Allowance for loan losses	$ (10,000)	$ (11,000)	$ (9,000)
Total loans (as a percent)	0.21%	0.23%