Investment securities (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Investment securities Estimated fair value, Less than 12 months	$ 34,114	$ 22,002
Investment securities Unrealized losses, Less than 12 months	43	246
Investment securities Estimated fair value, 12 months or more Total	15,468	5,245
Investment securities Unrealized losses,12 months or more Total	327	129
Investment securities Estimated fair value, Total	49,582	27,247
Investment securities Unrealized losses,Total	370	375
U.S. Agency MBS [Member]
Investment securities Estimated fair value, Less than 12 months	34,114	20,039
Investment securities Unrealized losses, Less than 12 months	43	203
Investment securities Estimated fair value, 12 months or more Total	12,718	3,428
Investment securities Unrealized losses,12 months or more Total	209	36
Investment securities Estimated fair value, Total	46,832	23,467
Investment securities Unrealized losses,Total	252	239
Non-agency MBS [Member]
Investment securities Estimated fair value, Less than 12 months		603
Investment securities Unrealized losses, Less than 12 months		6
Investment securities Estimated fair value, 12 months or more Total		0
Investment securities Unrealized losses,12 months or more Total		0
Investment securities Estimated fair value, Total		603
Investment securities Unrealized losses,Total		6
U.S. Agency asset-backed securities [Member]
Investment securities Estimated fair value, Less than 12 months	0	1,360
Investment securities Unrealized losses, Less than 12 months	0	37
Investment securities Estimated fair value, 12 months or more Total	2,750	1,817
Investment securities Unrealized losses,12 months or more Total	118	93
Investment securities Estimated fair value, Total	2,750	3,177
Investment securities Unrealized losses,Total	$ 118	$ 130