Fair Value of Financial Instruments - Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Assets:
Fair Value		$ 310,348
Equity securities, at fair value		2,320	$ 0	[1]
Securities available for sale, at fair value	[1]		321,337
Level 1
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Level 2
Assets:
Fair Value		310,348
Equity securities, at fair value		2,320
Securities available for sale, at fair value			321,337
Level 3
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Federal agencies and GSEs
Assets:
Fair Value		108,627
Securities available for sale, at fair value			112,127
Mortgage-backed and CMOs
Assets:
Fair Value		108,421
Securities available for sale, at fair value			105,316
State and municipal
Assets:
Fair Value		85,322
Securities available for sale, at fair value			93,626
Corporate
Assets:
Fair Value		7,978
Securities available for sale, at fair value			8,062
Equity securities
Assets:
Securities available for sale, at fair value			2,206
Fair Value, Measurements, Recurring
Assets:
Fair Value		310,348
Equity securities, at fair value		2,320
Securities available for sale, at fair value			321,337
Fair Value, Measurements, Recurring | Level 1
Assets:
Fair Value		0
Equity securities, at fair value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Level 2
Assets:
Fair Value		310,348
Equity securities, at fair value		2,320
Securities available for sale, at fair value			321,337
Fair Value, Measurements, Recurring | Level 3
Assets:
Fair Value		0
Equity securities, at fair value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Federal agencies and GSEs
Assets:
Fair Value		108,627
Securities available for sale, at fair value			112,127
Fair Value, Measurements, Recurring | Federal agencies and GSEs | Level 1
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Federal agencies and GSEs | Level 2
Assets:
Fair Value		108,627
Securities available for sale, at fair value			112,127
Fair Value, Measurements, Recurring | Federal agencies and GSEs | Level 3
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Mortgage-backed and CMOs
Assets:
Fair Value		108,421
Securities available for sale, at fair value			105,316
Fair Value, Measurements, Recurring | Mortgage-backed and CMOs | Level 1
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Mortgage-backed and CMOs | Level 2
Assets:
Fair Value		108,421
Securities available for sale, at fair value			105,316
Fair Value, Measurements, Recurring | Mortgage-backed and CMOs | Level 3
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | State and municipal
Assets:
Fair Value		85,322
Securities available for sale, at fair value			93,626
Fair Value, Measurements, Recurring | State and municipal | Level 1
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | State and municipal | Level 2
Assets:
Fair Value		85,322
Securities available for sale, at fair value			93,626
Fair Value, Measurements, Recurring | State and municipal | Level 3
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Corporate
Assets:
Fair Value		7,978
Securities available for sale, at fair value			8,062
Fair Value, Measurements, Recurring | Corporate | Level 1
Assets:
Fair Value		0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Corporate | Level 2
Assets:
Fair Value		7,978
Securities available for sale, at fair value			8,062
Fair Value, Measurements, Recurring | Corporate | Level 3
Assets:
Fair Value		$ 0
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Equity securities
Assets:
Securities available for sale, at fair value			2,206
Fair Value, Measurements, Recurring | Equity securities | Level 1
Assets:
Securities available for sale, at fair value			0
Fair Value, Measurements, Recurring | Equity securities | Level 2
Assets:
Securities available for sale, at fair value			2,206
Fair Value, Measurements, Recurring | Equity securities | Level 3
Assets:
Securities available for sale, at fair value			$ 0

[1] Derived from audited consolidated financial statements.