Earnings Per Share - Computation of earning per share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Basic earnings per share
Income available to common stockholders (in dollars)									$ 4,078	$ 3,650
Income available to common stockholders (in shares)									1,527,384	1,517,902
Income available to common stockholders (in dollars per share)	$ 0.67	$ 0.68	$ 0.72	$ 0.60	$ 1.17	$ 0.50	$ 0.40	$ 0.33	$ 2.67	$ 2.40
Effect of dilutive RRP awards and stock options (in shares)									5,064	2,005
Diluted earnings per share
Income available to common stockholders and assumed conversions (in dollars)									$ 4,078	$ 3,650
Income available to common stockholders and assumed conversions (in shares)									1,532,448	1,519,907
Income available to common stockholders and assumed conversions (in dollars per share)	$ 0.66	$ 0.68	$ 0.72	$ 0.60	$ 1.17	$ 0.50	$ 0.40	$ 0.33	$ 2.66	$ 2.40