Loans (Details 5) (USD $)	3 Months Ended		12 Months Ended				12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2012 item	Dec. 31, 2012 Grade 8 item	Mar. 31, 2012 Grade 8	Dec. 31, 2011 Grade 8	Dec. 31, 2012 Grade 9	Mar. 31, 2012 Grade 9	Dec. 31, 2011 Grade 9
Loans
The number of components in the general portion of the Company's allowance			2
Number of quarters whose historical average is used to calculate the historical loss ratio			20
Period of charge-off percentage based on which additional allocation is determined							1 year
Minimum additional reserve (as a percent)							3.00%	3.00%	3.25%
Number of quarters in more current measure of historical losses in adversely graded loans				12
Number of quarters in less current measure of historical losses in adversely graded loans				20
Minimum additional amount for loans (as a percent)				1.00%	1.00%	1.25%
Decrease in allowances	$ (2,600,000)	$ (4,400,000)