Investment Securities Held to Maturity (Details) $ in Thousands	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	$ 335,211	$ 345,427	$ 315,284
Held-To-Maturity Securities, at Fair Value	335,105	343,751	324,337
Gross Unrealized Gains	2,708	2,316	9,061
Gross Unrealized Losses	2,813	3,992	8
Held-To-Maturity Securities, Pledged as Collateral	316,966	321,202	299,767
Maturities of Debt Securities, at Amortized Cost:
Within One Year	29,743
From 1 - 5 Years	150,042
From 5 - 10 Years	151,667
Over 10 Years	3,758
Maturities of Debt Securities, at Fair Value:
Within One Year	29,788
From 1 - 5 Years	151,886
From 5 - 10 Years	149,675
Over 10 Years	3,756
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	103,132	120,561	4,293
12 Months or Longer	657	12,363	658
Total	$ 103,789	$ 132,924	$ 4,951
Number of Securities in a Continuous Loss Position	259	360	8
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 2,810	$ 3,298	$ 6
12 Months or Longer	3	694	2
Total	2,813	3,992	8
State and Municipal Obligations
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	263,642	268,892	224,831
Held-To-Maturity Securities, at Fair Value	263,255	267,127	231,598
Gross Unrealized Gains	2,410	2,058	6,769
Gross Unrealized Losses	2,796	3,823	2
Maturities of Debt Securities, at Amortized Cost:
Within One Year	29,743
From 1 - 5 Years	85,621
From 5 - 10 Years	144,519
Over 10 Years	3,758
Maturities of Debt Securities, at Fair Value:
Within One Year	29,788
From 1 - 5 Years	87,239
From 5 - 10 Years	142,472
Over 10 Years	3,756
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	95,450	107,255	648
12 Months or Longer	657	12,363	658
Total	$ 96,107	$ 119,618	$ 1,306
Number of Securities in a Continuous Loss Position	251	347	7
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 2,793	$ 3,129	$ 0
12 Months or Longer	3	694	2
Total	2,796	3,823	2
Mortgage-Backed Securities - Residential
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	71,569	75,535	89,453
Held-To-Maturity Securities, at Fair Value	71,850	75,624	91,739
Gross Unrealized Gains	298	258	2,292
Gross Unrealized Losses	17	169	6
Maturities of Debt Securities, at Amortized Cost:
Within One Year	0
From 1 - 5 Years	64,421
From 5 - 10 Years	7,148
Over 10 Years	0
Maturities of Debt Securities, at Fair Value:
Within One Year	0
From 1 - 5 Years	64,647
From 5 - 10 Years	7,203
Over 10 Years	0
Securities in a Continuous Loss Position, at Fair Value:
Less than 12 Months	7,682	13,306	3,645
12 Months or Longer	0	0	0
Total	$ 7,682	$ 13,306	$ 3,645
Number of Securities in a Continuous Loss Position	8	13	1
Unrealized Losses on Securities in a Continuous Loss Position:
Less than 12 Months	$ 17	$ 169	$ 6
12 Months or Longer	0	0	0
Total	17	169	6
Mortgage-Backed Securities - Residential | Agency Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	3,106	3,206	3,674
Mortgage-Backed Securities - Residential | US Government-sponsored Enterprises Debt Securities
Schedule of Held-to-maturity Securities [Line Items]
Held-to-Maturity at Amortized Cost	68,463	72,329	85,779
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	68,729	72,402	87,945
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	$ 3,794