Debt Securities - Summary of securities in unrealized loss position (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value
Less Than 12 Months	$ 28,712	$ 80,822
12 Months or Longer	101,272	41,160
Total	129,984	121,982
Gross Unrealized Losses
Less Than 12 Months	(172)	(711)
12 Months or Longer	(3,474)	(1,228)
Total	(3,646)	(1,939)
Mortgage-backed securities - agency
Fair Value
Less Than 12 Months	9,528	5,766
12 Months or Longer	15,497	12,312
Total	25,025	18,078
Gross Unrealized Losses
Less Than 12 Months	(99)	(26)
12 Months or Longer	(625)	(265)
Total	(724)	(291)
Collateralized mortgage obligations (CMO's) - agency
Fair Value
Less Than 12 Months	19,184	75,056
12 Months or Longer	85,775	28,848
Total	104,959	103,904
Gross Unrealized Losses
Less Than 12 Months	(73)	(685)
12 Months or Longer	(2,849)	(963)
Total	$ (2,922)	$ (1,648)