Regulatory Matters (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Regulatory Matters [Abstract]
Required Reserve Balances with Federal Reserve Bank	$ 17,700	$ 17,000
Regulatory Capital Requirements
Statutory Accounting Practices, Statutory Amount Available for Dividend Payments with Regulatory Approval	24,000
Holding Company
Regulatory Capital Requirements
Common Equity Tier 1 Capital	$ 332,774	$ 306,506
Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	13.50%	12.90%
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy	$ 111,303	$ 106,801
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized	$ 160,772	$ 154,268
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Risk Based Capital	$ 339,881	$ 313,430
Tier One Risk Based Capital to Risk Weighted Assets	13.70%	13.20%
Tier One Risk Based Capital Required for Capital Adequacy	$ 148,405	$ 142,402
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Tier One Risk Based Capital Required to be Well Capitalized	$ 197,873	$ 189,869
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Capital	$ 361,579	$ 334,957
Capital to Risk Weighted Assets	14.60%	14.10%
Capital Required for Capital Adequacy	$ 197,843	$ 189,869
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Capital Required to be Well Capitalized	$ 247,341	$ 237,336
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Leverage Capital	$ 339,881	$ 313,430
Tier One Leverage Capital to Average Assets	9.90%	9.70%
Tier One Leverage Capital Required for Capital Adequacy	$ 137,343	$ 129,803
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 171,679	$ 162,254
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Risk Weighted Assets	$ 2,473,329	$ 2,373,359
Bank
Regulatory Capital Requirements
Common Equity Tier 1 Capital	$ 310,818	$ 271,319
Common Equity Tier 1 Risk Based Capital to Risk Weighted Assets	12.60%	11.50%
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy	$ 110,955	$ 106,474
Common Equity Tier 1 Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized	$ 160,268	$ 153,795
Common Equity Tier 1 Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	6.50%	6.50%
Tier One Risk Based Capital	$ 310,818	$ 291,319
Tier One Risk Based Capital to Risk Weighted Assets	12.60%	12.30%
Tier One Risk Based Capital Required for Capital Adequacy	$ 147,940	$ 141,965
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Tier One Risk Based Capital Required to be Well Capitalized	$ 197,254	$ 189,287
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Capital	$ 329,611	$ 309,749
Capital to Risk Weighted Assets	13.40%	13.10%
Capital Required for Capital Adequacy	$ 197,254	$ 189,287
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Capital Required to be Well Capitalized	$ 246,567	$ 236,608
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Leverage Capital	$ 310,818	$ 291,319
Tier One Leverage Capital to Average Assets	9.10%	9.00%
Tier One Leverage Capital Required for Capital Adequacy	$ 137,163	$ 129,633
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Tier One Leverage Capital Required to be Well Capitalized	$ 171,454	$ 162,041
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%
Risk Weighted Assets	$ 2,465,653	$ 2,366,082