Fair Value of Financial Instruments (Fair Values of Financial Assets and Liabilities on Balance Sheets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018	Sep. 30, 2017
Fair Value
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	$ 28,132	$ 28,132
Cash and Cash Equivalents, Fair Value Disclosure	72,194	72,629
Unrealized Gain (Loss) on Investments	6,500
Held-to-maturity Securities, Fair Value	41,213	39,440
Financial assets:
Bank premises and equipment, net	52,510	56,247
Bank owned life insurance	62,176	62,644	$ 62,644
Financial liabilities:
Federal Reserve Bank Stock	10,179	10,179
Loans Receivable and Loans Held-for-sale, Fair Value Disclosure	2,274,194	2,297,373
Servicing Asset	2,305	2,303
Deposits, Fair Value Disclosure	2,730,071	2,809,738
Short-term Debt, Fair Value	209,628	203,494
Long-term Debt, Fair Value	142,108	119,817
Carrying Amount
Financial liabilities:
Other Investments	38,371	39,285
Loans Receivable and Loans Held-for-sale, Fair Value Disclosure	2,338,344	2,383,530
Deposits, Fair Value Disclosure	2,730,330	2,813,181
Short-term Debt, Fair Value	209,491	203,475
Long-term Debt, Fair Value	144,019	123,481
Level 2
Fair Value
Held-to-maturity Securities, Fair Value	41,213	39,440
Financial liabilities:
Other Investments	38,371	39,285
Commercial mortgage-backed securities | Level 2
Fair Value
Held-to-maturity Securities, Fair Value	4,569	4,162
Commercial mortgage-backed securities | Level 1
Fair Value
Held-to-maturity Securities, Fair Value	0	0
Residential mortgage-backed securities | Level 2
Fair Value
Held-to-maturity Securities, Fair Value	32,227	30,978
Residential mortgage-backed securities | Level 1
Fair Value
Held-to-maturity Securities, Fair Value	0	0
States and political subdivisions | Level 2
Fair Value
Held-to-maturity Securities, Fair Value	4,417	4,300
States and political subdivisions | Level 1
Fair Value
Held-to-maturity Securities, Fair Value	0	0
Commercial mortgage-backed securities
Fair Value
Held-to-maturity Securities, Fair Value	4,569	4,162
Residential mortgage-backed securities
Fair Value
Held-to-maturity Securities, Fair Value	32,227	30,978
States and political subdivisions
Fair Value
Held-to-maturity Securities, Fair Value	4,417	4,300
Recurring Basis [Member] | Level 2
Fair Value
Investment in Federal Home Loan Bank Stock, Fair Value Disclosure	28,132	28,132
Financial liabilities:
Federal Reserve Bank Stock	10,179	10,179
Recurring Basis [Member] | Non-qualified deferred comp
Financial liabilities:
Other Investments		914
Recurring Basis [Member] | FHLMC stock
Financial liabilities:
Other Investments		$ 60
Recurring Basis [Member] | FHLMC stock | Level 2
Financial liabilities:
Other Investments	$ 60