Securities (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) Security	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 493,561		$ 523,520
Unrealized Gains	1,978		3,197
Unrealized Losses	6,420		3,792
Fair Value	489,119		522,925
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	224,325		153,090
Less Than Twelve Months, Unrealized Losses	3,085		1,400
Twelve Months or More, Fair Value	101,582		108,033
Twelve Months or More, Unrealized Losses	3,335		2,392
Total, Fair Value	325,907		261,123
Total, Unrealized Losses	6,420		3,792
Private Label Mortgage Backed Securities Below Investment Grade [Abstract]
Fair value	1,975
Amortized cost	1,609
Non-credit unrealized loss	0
Unrealized gain	366
Cumulative credit related OTTI	1,594
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Balance at beginning of period	1,594	$ 1,594	1,594
Additions to credit losses on securities for which no previous OTTI was recognized	0	0
Increases to credit losses on securities for which OTTI was previously recognized	0	0
Balance at end of period	1,594	1,594	1,594
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Maturing within one year	27,598
Maturing after one year but within five years	76,940
Maturing after five years but within ten years	68,816
Maturing after ten years	52,470
Available-for-sale securities, debt maturities, amortized cost basis	225,824
U.S. agency residential mortgage-backed	138,270
U.S. agency commercial mortgage-backed	10,218
Private label mortgage-backed	28,690
Other asset backed	90,559
Total	493,561
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Maturing within one year	27,580
Maturing after one year but within five years	76,334
Maturing after five years but within ten years	67,803
Maturing after ten years	51,235
Total available-for-sale securities fair value	222,952
U.S. agency residential mortgage-backed	137,244
U.S. agency commercial mortgage-backed	9,945
Private label mortgage-backed	28,451
Other asset backed	90,527
Total	489,119
Gain and losses realized on sale of securities available for sale [Abstract]
Proceeds	22,277	6,152
Realized gains	76	106
Realized losses	95	0
Credit related OTTI recognized in earnings	0	0
Trading securities, realized losses	(154)	$ (79)
U.S. Treasury [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	600		898
Unrealized Gains	0		0
Unrealized Losses	1		0
Fair Value	599		898
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	599
Less Than Twelve Months, Unrealized Losses	1
Twelve Months or More, Fair Value	0
Twelve Months or More, Unrealized Losses	0
Total, Fair Value	599
Total, Unrealized Losses	$ 1
Number of securities with market fair value less than amortized cost | Security	1
U.S. Agency [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 24,067		25,667
Unrealized Gains	15		82
Unrealized Losses	146		67
Fair Value	23,936		25,682
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	13,958		5,466
Less Than Twelve Months, Unrealized Losses	101		26
Twelve Months or More, Fair Value	5,556		5,735
Twelve Months or More, Unrealized Losses	45		41
Total, Fair Value	19,514		11,201
Total, Unrealized Losses	$ 146		67
Number of securities with market fair value less than amortized cost | Security	43
U.S. Agency Residential Mortgage-Backed [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 138,270		137,785
Unrealized Gains	925		1,116
Unrealized Losses	1,951		983
Fair Value	137,244		137,918
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	44,450		22,198
Less Than Twelve Months, Unrealized Losses	877		229
Twelve Months or More, Fair Value	31,930		40,698
Twelve Months or More, Unrealized Losses	1,074		754
Total, Fair Value	76,380		62,896
Total, Unrealized Losses	$ 1,951		983
Number of securities with market fair value less than amortized cost | Security	134
U.S. Agency Commercial Mortgage-Backed [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 10,218		9,894
Unrealized Gains	1		36
Unrealized Losses	274		170
Fair Value	9,945		9,760
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	5,775		2,181
Less Than Twelve Months, Unrealized Losses	82		34
Twelve Months or More, Fair Value	4,025		3,994
Twelve Months or More, Unrealized Losses	192		136
Total, Fair Value	9,800		6,175
Total, Unrealized Losses	$ 274		170
Number of securities with market fair value less than amortized cost | Security	18
Private Label Mortgage-Backed [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 28,690		29,011
Unrealized Gains	397		428
Unrealized Losses	636		330
Fair Value	28,451		29,109
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	15,248		11,390
Less Than Twelve Months, Unrealized Losses	349		92
Twelve Months or More, Fair Value	4,263		4,396
Twelve Months or More, Unrealized Losses	287		238
Total, Fair Value	19,511		15,786
Total, Unrealized Losses	$ 636		330
Number of securities with market fair value less than amortized cost | Security	27
Private Label Mortgage Backed Securities Below Investment Grade [Abstract]
Number of private label mortgage backed securities complete recovery of cost basis | Security	2
Number of private label mortgage backed securities currently with OTTI unrealized gains | Security	3
Senior Security [Member]
Private Label Mortgage Backed Securities Below Investment Grade [Abstract]
Fair value	$ 996
Amortized cost	853
Non-credit unrealized loss	0
Unrealized gain	143
Cumulative credit related OTTI	757
Super Senior Security [Member]
Private Label Mortgage Backed Securities Below Investment Grade [Abstract]
Fair value	921
Amortized cost	756
Non-credit unrealized loss	0
Unrealized gain	165
Cumulative credit related OTTI	457
Senior Support Security [Member]
Private Label Mortgage Backed Securities Below Investment Grade [Abstract]
Fair value	58
Amortized cost	0
Non-credit unrealized loss	0
Unrealized gain	58
Cumulative credit related OTTI	380
Other Asset Backed [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	90,559		93,811
Unrealized Gains	165		202
Unrealized Losses	197		115
Fair Value	90,527		93,898
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	37,043		20,352
Less Than Twelve Months, Unrealized Losses	97		40
Twelve Months or More, Fair Value	13,897		16,648
Twelve Months or More, Unrealized Losses	100		75
Total, Fair Value	50,940		37,000
Total, Unrealized Losses	$ 197		115
Number of securities with market fair value less than amortized cost | Security	103
Obligations of States and Political Subdivisions [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 154,194		174,073
Unrealized Gains	336		755
Unrealized Losses	2,707		1,883
Fair Value	151,823		172,945
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	85,527		76,574
Less Than Twelve Months, Unrealized Losses	1,323		936
Twelve Months or More, Fair Value	33,654		28,246
Twelve Months or More, Unrealized Losses	1,384		947
Total, Fair Value	119,181		104,820
Total, Unrealized Losses	$ 2,707		1,883
Number of securities with market fair value less than amortized cost | Security	382
Corporate [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 41,954		47,365
Unrealized Gains	139		578
Unrealized Losses	344		90
Fair Value	41,749		47,853
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	21,244		14,440
Less Than Twelve Months, Unrealized Losses	237		33
Twelve Months or More, Fair Value	3,893		3,943
Twelve Months or More, Unrealized Losses	107		57
Total, Fair Value	25,137		18,383
Total, Unrealized Losses	$ 344		90
Number of securities with market fair value less than amortized cost | Security	26
Trust Preferred [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	$ 2,931		2,929
Unrealized Gains	0		0
Unrealized Losses	121		127
Fair Value	2,810		2,802
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	0		0
Less Than Twelve Months, Unrealized Losses	0		0
Twelve Months or More, Fair Value	2,810		2,802
Twelve Months or More, Unrealized Losses	121		127
Total, Fair Value	2,810		2,802
Total, Unrealized Losses	$ 121		127
Number of securities with market fair value less than amortized cost | Security	3
Number of issues rated as investment grade | Security	2
Number of major credit rating agencies rating securities with fair value less than amortized cost | Security	2
Number of securities non-rated | Security	1
Non-rated trust preferred securities, amortized cost	$ 1,000
Non-rated trust preferred securities, fair value	900
Rated Issues [Member]
Trust preferred securities [Abstract]
Fair Value	1,875		1,860
Net Unrealized Loss	(56)		(69)
Unrated Issues [Member]
Trust preferred securities [Abstract]
Fair Value	935		942
Net Unrealized Loss	(65)		(58)
Foreign Government [Member]
Available-for-sale Securities, Amortized Cost Basis [Abstract]
Amortized Cost	2,078		2,087
Unrealized Gains	0		0
Unrealized Losses	43		27
Fair Value	2,035		2,060
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less Than Twelve Months, Fair Value	481		489
Less Than Twelve Months, Unrealized Losses	18		10
Twelve Months or More, Fair Value	1,554		1,571
Twelve Months or More, Unrealized Losses	25		17
Total, Fair Value	2,035		2,060
Total, Unrealized Losses	$ 43		$ 27
Number of securities with market fair value less than amortized cost | Security	2