Securities, Securities in Continuous Unrealized Loss Position (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) Security	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) Security Bond	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	$ 49,957		$ 49,957		$ 37,066
Less than 12 months, unrealized (losses)	(1,250)		(1,250)		(394)
12 months or more, fair value	9,842		9,842		11,548
12 months or more, unrealized (losses)	(474)		(474)		(431)
Total, fair value	59,799		59,799		48,614
Total, unrealized (losses)	$ (1,724)		$ (1,724)		(825)
Impaired Securities [Abstract]
Number of securities in a loss position | Security	70		70
Corporate bonds with cost basis net of other-than-temporary impairment	$ 74,527		$ 74,527		72,198
Estimated maturity			16 years
Anniversary on which securities could have been called at par			5 years
Frequency of repricing			3 months
Interest income	6,540	$ 5,713	$ 12,910	$ 11,128
LIBOR [Member]
Impaired Securities [Abstract]
Term of variable rate			3 months
Obligations of U.S. Government Corporations and Agencies [Member]
Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	42,118		$ 42,118		32,512
Less than 12 months, unrealized (losses)	(1,089)		(1,089)		(330)
12 months or more, fair value	9,255		9,255		10,008
12 months or more, unrealized (losses)	(454)		(454)		(278)
Total, fair value	51,373		51,373		42,520
Total, unrealized (losses)	(1,543)		(1,543)		(608)
Impaired Securities [Abstract]
Corporate bonds with cost basis net of other-than-temporary impairment	59,153		59,153		52,872
Obligations of States and Political Subdivisions [Member]
Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value	7,839		7,839		4,172
Less than 12 months, unrealized (losses)	(161)		(161)		(60)
12 months or more, fair value	587		587		0
12 months or more, unrealized (losses)	(20)		(20)		0
Total, fair value	8,426		8,426		4,172
Total, unrealized (losses)	(181)		(181)		(60)
Impaired Securities [Abstract]
Corporate bonds with cost basis net of other-than-temporary impairment	$ 14,705		$ 14,705		15,124
Corporate Bonds [Member]
Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value					0
Less than 12 months, unrealized (losses)					0
12 months or more, fair value					1,540
12 months or more, unrealized (losses)					(153)
Total, fair value					1,540
Total, unrealized (losses)					(153)
Impaired Securities [Abstract]
Number of impaired securities | Security	1		1
Corporate bonds with cost basis net of other-than-temporary impairment	$ 669		$ 669		3,816
Interest income	28	$ 53	$ 79	$ 104
Corporate Bonds [Member] | Performing [Member]
Impaired Securities [Abstract]
Bonds classified as performing | Bond			1
Mutual Funds [Member]
Securities in Continuous Unrealized Loss Position [Abstract]
Less than 12 months, fair value					382
Less than 12 months, unrealized (losses)					(4)
12 months or more, fair value					0
12 months or more, unrealized (losses)					0
Total, fair value					382
Total, unrealized (losses)					(4)
Impaired Securities [Abstract]
Corporate bonds with cost basis net of other-than-temporary impairment					$ 386
1 Corporate Bond [Member]
Impaired Securities [Abstract]
Face value of corporate bond	2,000		$ 2,000
Gain realized on corporate bond due to auction and settlement	303
2 Corporate Bond [Member]
Impaired Securities [Abstract]
Face value of corporate bond	$ 4,000		4,000
Gain realized on corporate bond due to auction and settlement			$ 838