Investment Securities - Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investment securities
Fair value, less than twelve months	$ 52,687	$ 58,552
Gross unrealized losses, less than twelve months	(1,382)	(1,934)
Fair value, twelve months or greater	13,391	16,623
Gross unrealized losses, twelve months or greater	(717)	(988)
Fair value, total	66,078	75,175
Gross unrealized losses, total	(2,099)	(2,922)
Mortgage-backed securities
Investment securities
Fair value, less than twelve months	3,480	3,572
Gross unrealized losses, less than twelve months	(113)	(106)
Fair value, twelve months or greater	0	3,627
Gross unrealized losses, twelve months or greater	0	(58)
Fair value, total	3,480	7,199
Gross unrealized losses, total	(113)	(164)
Asset-backed securities
Investment securities
Fair value, less than twelve months	0	0
Gross unrealized losses, less than twelve months	0	0
Fair value, twelve months or greater	0	0
Gross unrealized losses, twelve months or greater	0	0
Fair value, total	0	0
Gross unrealized losses, total	0	0
State and political securities
Investment securities
Fair value, less than twelve months	18,292	26,113
Gross unrealized losses, less than twelve months	(237)	(509)
Fair value, twelve months or greater	0	0
Gross unrealized losses, twelve months or greater	0	0
Fair value, total	18,292	26,113
Gross unrealized losses, total	(237)	(509)
Other debt securities
Investment securities
Fair value, less than twelve months	29,664	28,140
Gross unrealized losses, less than twelve months	(983)	(1,179)
Fair value, twelve months or greater	13,391	12,240
Gross unrealized losses, twelve months or greater	(717)	(886)
Fair value, total	43,055	40,380
Gross unrealized losses, total	(1,700)	(2,065)
Debt securities
Investment securities
Fair value, less than twelve months	51,436	57,825
Gross unrealized losses, less than twelve months	(1,333)	(1,794)
Fair value, twelve months or greater	13,391	15,867
Gross unrealized losses, twelve months or greater	(717)	(944)
Fair value, total	64,827	73,692
Gross unrealized losses, total	(2,050)	(2,738)
Financial institution equity securities
Investment securities
Fair value, less than twelve months	0	0
Gross unrealized losses, less than twelve months	0	0
Fair value, twelve months or greater	0	0
Gross unrealized losses, twelve months or greater	0	0
Fair value, total	0	0
Gross unrealized losses, total	0	0
Non-financial institution equity securities
Investment securities
Fair value, less than twelve months	1,251	727
Gross unrealized losses, less than twelve months	(49)	(140)
Fair value, twelve months or greater	0	756
Gross unrealized losses, twelve months or greater	0	(44)
Fair value, total	1,251	1,483
Gross unrealized losses, total	(49)	(184)
Other equity securities
Investment securities
Fair value, less than twelve months	1,251	727
Gross unrealized losses, less than twelve months	(49)	(140)
Fair value, twelve months or greater	0	756
Gross unrealized losses, twelve months or greater	0	(44)
Fair value, total	1,251	1,483
Gross unrealized losses, total	$ (49)	$ (184)