Investment securities (Available For Sale Securities Continuous Unrealized Loss Position Fair Value) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale
Estimated fair value, Less than 12 months	$ 270,224	$ 90,042
Unrealized losses, Less than 12 months	(4,354)	(888)
Estimated fair value, 12 months or more	5,584	48,322
Unrealized losses, 12 months or more	(210)	(606)
Estimated fair value, Total	275,808	138,364
Unrealized losses, Total	(4,564)	(1,494)
Held-to-maturity
Estimated fair value, Less than 12 months	9,583	2,788
Unrealized losses, Less than 12 months	(250)	(7)
Estimated fair value, 12 months or more	0	0
Unrealized losses, 12 months or more	0	0
Estimated fair value, Total	9,583	2,788
Unrealized losses, Total	(250)	(7)
U.S. Agency (MBS)
Available-for-sale
Estimated fair value, Less than 12 months	51,082	23,630
Unrealized losses, Less than 12 months	(786)	(123)
Estimated fair value, 12 months or more	1,733	34,576
Unrealized losses, 12 months or more	(13)	(332)
Estimated fair value, Total	52,815	58,206
Unrealized losses, Total	(799)	(455)
Held-to-maturity
Estimated fair value, Less than 12 months	7,641	2,063
Unrealized losses, Less than 12 months	(148)	(5)
Estimated fair value, 12 months or more	0	0
Unrealized losses, 12 months or more	0	0
Estimated fair value, Total	7,641	2,063
Unrealized losses, Total	(148)	(5)
Non-agency MBS
Available-for-sale
Estimated fair value, Less than 12 months	211,909	66,412
Unrealized losses, Less than 12 months	(3,268)	(765)
Estimated fair value, 12 months or more	1,933	12,225
Unrealized losses, 12 months or more	(140)	(251)
Estimated fair value, Total	213,842	78,637
Unrealized losses, Total	(3,408)	(1,016)
U.S. Agency asset-backed securities
Available-for-sale
Estimated fair value, Less than 12 months	0	0
Unrealized losses, Less than 12 months	0	0
Estimated fair value, 12 months or more	1,918	1,521
Unrealized losses, 12 months or more	(57)	(23)
Estimated fair value, Total	1,918	1,521
Unrealized losses, Total	(57)	(23)
Corporate securities
Available-for-sale
Estimated fair value, Less than 12 months	6,709
Unrealized losses, Less than 12 months	(287)
Estimated fair value, 12 months or more	0
Unrealized losses, 12 months or more	0
Estimated fair value, Total	6,709
Unrealized losses, Total	(287)
Mutual fund
Available-for-sale
Estimated fair value, Less than 12 months	524
Unrealized losses, Less than 12 months	(13)
Estimated fair value, 12 months or more	0
Unrealized losses, 12 months or more	0
Estimated fair value, Total	524
Unrealized losses, Total	(13)
Obligations of state and political subdivisions
Held-to-maturity
Estimated fair value, Less than 12 months	1,942	725
Unrealized losses, Less than 12 months	(102)	(2)
Estimated fair value, 12 months or more	0	0
Unrealized losses, 12 months or more	0	0
Estimated fair value, Total	1,942	725
Unrealized losses, Total	$ (102)	$ (2)