Investment Securities Held to Maturity (Details) $ in Thousands	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	$ 348,018	$ 345,427	$ 343,814
Held-To-Maturity Securities, at Fair Value	350,355	343,751	354,778
Gross Unrealized Gains	3,885	2,316	10,965
Gross Unrealized Losses	1,548	3,992	1
Held-To-Maturity Securities, Pledged as Collateral	327,820	321,202	327,820
Maturities of Debt Securities, at Amortized Cost:
Within One Year	13,986
From 1 - 5 Years	152,578
From 5 - 10 Years	170,188
Over 10 Years	11,266
Maturities of Debt Securities, at Fair Value:
Within One Year	14,006
From 1 - 5 Years	154,627
From 5 - 10 Years	170,519
Over 10 Years	11,203
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	97,384	120,561	0
12 Months or Longer	403	12,363	659
Total	$ 97,787	$ 132,924	$ 659
Number of Securities in a Continuous Loss Position	272	360	3
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 1,546	$ 3,298	$ 0
12 Months or Longer	2	694	1
Total	1,548	3,992	1
State and Municipal Obligations
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	280,485	268,892	257,982
Held-To-Maturity Securities, at Fair Value	282,157	267,127	265,983
Gross Unrealized Gains	3,208	2,058	8,002
Gross Unrealized Losses	1,536	3,823	1
Maturities of Debt Securities, at Amortized Cost:
Within One Year	13,986
From 1 - 5 Years	91,072
From 5 - 10 Years	164,161
Over 10 Years	11,266
Maturities of Debt Securities, at Fair Value:
Within One Year	14,006
From 1 - 5 Years	92,549
From 5 - 10 Years	164,399
Over 10 Years	11,203
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	93,046	107,255	0
12 Months or Longer	403	12,363	659
Total	$ 93,449	$ 119,618	$ 659
Number of Securities in a Continuous Loss Position	263	347	3
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 1,534	$ 3,129	$ 0
12 Months or Longer	2	694	1
Total	1,536	3,823	1
Mortgage-Backed Securities - Residential
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	67,533	75,535	84,832
Held-To-Maturity Securities, at Fair Value	68,198	75,624	87,795
Gross Unrealized Gains	677	258	2,963
Gross Unrealized Losses	12	169	0
Maturities of Debt Securities, at Amortized Cost:
Within One Year	0
From 1 - 5 Years	61,506
From 5 - 10 Years	6,027
Over 10 Years	0
Maturities of Debt Securities, at Fair Value:
Within One Year	0
From 1 - 5 Years	62,078
From 5 - 10 Years	6,120
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	4,338	13,306	0
12 Months or Longer	0	0	0
Total	$ 4,338	$ 13,306	$ 0
Number of Securities in a Continuous Loss Position	9	13	0
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 12	$ 169	$ 0
12 Months or Longer	0	0	0
Total	12	169	0
Mortgage-Backed Securities - Residential | Agency Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	3,106	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	64,427	72,329	81,335
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	65,077	72,402	84,173
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	$ 3,121	$ 3,222	$ 3,622