Investment Securities Held to Maturity (Details) $ in Thousands	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	$ 341,526	$ 345,427	$ 338,238
Held-To-Maturity Securities, at Fair Value	343,899	343,751	347,441
Gross Unrealized Gains	3,715	2,316	9,273
Gross Unrealized Losses	1,342	3,992	70
Held-To-Maturity Securities, Pledged as Collateral	325,096	321,202	321
Maturities of Debt Securities, at Amortized Cost:
Within One Year	39,609
From 1 - 5 Years	133,916
From 5 - 10 Years	164,265
Over 10 Years	3,736
Maturities of Debt Securities, at Fair Value:
Within One Year	39,782
From 1 - 5 Years	136,064
From 5 - 10 Years	164,287
Over 10 Years	3,766
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	81,782	120,561	11,891
12 Months or Longer	13,331	12,363	1,172
Total	$ 95,113	$ 132,924	$ 13,063
Number of Securities in a Continuous Loss Position	259	360	3
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 1,045	$ 3,298	$ 68
12 Months or Longer	297	694	2
Total	1,342	3,992	70
State and Municipal Obligations
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	277,738	268,892	257,255
Held-To-Maturity Securities, at Fair Value	279,384	267,127	263,897
Gross Unrealized Gains	2,977	2,058	6,712
Gross Unrealized Losses	1,331	3,823	70
Maturities of Debt Securities, at Amortized Cost:
Within One Year	39,609
From 1 - 5 Years	79,412
From 5 - 10 Years	154,981
Over 10 Years	3,736
Maturities of Debt Securities, at Fair Value:
Within One Year	39,782
From 1 - 5 Years	80,944
From 5 - 10 Years	154,892
Over 10 Years	3,766
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	78,238	107,255	11,891
12 Months or Longer	13,331	12,363	1,172
Total	$ 91,569	$ 119,618	$ 13,063
Number of Securities in a Continuous Loss Position	252	347	3
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 1,034	$ 3,129	$ 68
12 Months or Longer	297	694	2
Total	1,331	3,823	70
Mortgage-Backed Securities - Residential
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	63,788	75,535	79,983
Held-To-Maturity Securities, at Fair Value	64,515	75,624	82,544
Gross Unrealized Gains	738	258	2,561
Gross Unrealized Losses	11	169	0
Maturities of Debt Securities, at Amortized Cost:
Within One Year	0
From 1 - 5 Years	54,504
From 5 - 10 Years	9,284
Over 10 Years	0
Maturities of Debt Securities, at Fair Value:
Within One Year	0
From 1 - 5 Years	55,120
From 5 - 10 Years	9,395
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	3,544	13,306	0
12 Months or Longer	0	0	0
Total	$ 3,544	$ 13,306	$ 0
Number of Securities in a Continuous Loss Position	7	13	0
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 11	$ 169	$ 0
12 Months or Longer	0	0	0
Total	11	169	0
Mortgage-Backed Securities - Residential | Agency Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	2,792	3,206	3,497
Mortgage-Backed Securities - Residential | US Government-sponsored Enterprises Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	60,996	72,329	76,486
Corporate and Other Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	0	1,000	1,000
Held-To-Maturity Securities, at Fair Value	0	1,000	1,000
Gross Unrealized Gains	0	0	0
Gross Unrealized Losses	0	0	0
Maturities of Debt Securities, at Amortized Cost:
Within One Year	0
From 1 - 5 Years	0
From 5 - 10 Years	0
Over 10 Years	0
Maturities of Debt Securities, at Fair Value:
Within One Year	0
From 1 - 5 Years	0
From 5 - 10 Years	0
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	0	0	0
12 Months or Longer	0	0	0
Total	$ 0	$ 0	$ 0
Number of Securities in a Continuous Loss Position	0	0	0
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 0	$ 0	$ 0
12 Months or Longer	0	0	0
Total	0	0	0
Fair Value, Measurements, Recurring | Mortgage-Backed Securities - Residential | US Government-sponsored Enterprises Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-To-Maturity Securities, at Fair Value	61,716	72,402	78,922
Fair Value, Measurements, Recurring | Agency Securities | Mortgage-Backed Securities - Residential
Schedule of Held-to-maturity Securities [Line Items]
Held-To-Maturity Securities, at Fair Value	$ 2,799	$ 3,222	$ 3,622