Commitments and Contingencies (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($)
Other Commitments [Line Items]
VISA Class B Conversion Ratio	1.6298
Commitments to extend credit: | Home equity
Other Commitments [Line Items]
Contractual obligations	$ 201,009	$ 194,477
Commitments to extend credit: | Commercial real estate
Other Commitments [Line Items]
Contractual obligations	47,912	66,901
Commitments to extend credit: | Other commitments
Other Commitments [Line Items]
Contractual obligations	182,139	184,895
Standby letters of credit
Other Commitments [Line Items]
Contractual obligations	7,057	7,151
Commercial letters of credit
Other Commitments [Line Items]
Contractual obligations	$ 842	$ 831
Common Class B [Member] | VISA, Inc. (VISA)
Other Commitments [Line Items]
Investment Owned, Balance, Shares | shares	86,605
Common Class A [Member] | VISA, Inc. (VISA)
Other Commitments [Line Items]
Share Price | $ / shares	$ 150.09
Investment Owned, at Fair Value	$ 21,200