2. Investment securities, Continuous Unrealized Loss Position (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Investment securities with continuous unrealized loss position
Less than 12 Months, Fair Value	$ 124,554	$ 62,053
Less than 12 Months, Unrealized Losses	5,700	656
12 Months or More, Fair Value	10,173	12,913
12 Months or More, Unrealized Losses	101	138
Total, Fair Value	134,727	74,966
Total, Unrealized Losses	5,801	794
Mortgage-backed securities
Investment securities with continuous unrealized loss position
Less than 12 Months, Fair Value	45,774	48,126
Less than 12 Months, Unrealized Losses	596	468
12 Months or More, Fair Value	10,173	12,913
12 Months or More, Unrealized Losses	101	138
Total, Fair Value	55,947	61,039
Total, Unrealized Losses	697	606
U.S. Government sponsored enterprises
Investment securities with continuous unrealized loss position
Less than 12 Months, Fair Value	1,078	3,402
Less than 12 Months, Unrealized Losses	9	80
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total, Fair Value	1,078	3,402
Total, Unrealized Losses	9	80
State and political subdivisions
Investment securities with continuous unrealized loss position
Less than 12 Months, Fair Value	76,195	9,490
Less than 12 Months, Unrealized Losses	5,032	104
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total, Fair Value	76,195	9,490
Total, Unrealized Losses	5,032	104
Corporate bonds
Investment securities with continuous unrealized loss position
Less than 12 Months, Fair Value	1,507	1,035
Less than 12 Months, Unrealized Losses	63	4
12 Months or More, Fair Value	0	0
12 Months or More, Unrealized Losses	0	0
Total, Fair Value	1,507	1,035
Total, Unrealized Losses	$ 63	$ 4