Investments - Textual (Details)	1 Months Ended	3 Months Ended			9 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) security	Sep. 30, 2017 USD ($) security investment	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($) security	Sep. 30, 2017 USD ($) security investment	Sep. 30, 2016 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)
Schedule of Available-for-sale Securities
Available-for-sale Securities pledged as collateral		$ 96,042,000			$ 96,042,000
Unrealized gain (loss) of available-for sale securities		7,600,000			7,600,000			$ (891,000)
AOCI available-for-sale securities adjustment tax		3,195,000			3,195,000			(375,000)
Transfer of securities from available-for-sale to held-to-maturity				$ 8,500,000			$ 31,000,000
Fair value of held-to-maturity investment securities transferred	$ 23,100,000			$ 23,100,000			32,000,000
Unrealized gain on transfer of securities from available-for-sale to held-to-maturity							$ 163,000
Held-to-maturity securities, number of securities sold | security				5
Investments, number of securities sold | security				13
Gross realized gains from sales or calls		0	$ 0	$ 696,000	0	$ 696,000
Income tax impact from the reclassification of unrealized net gains on available-for-sale securities to realized net gains on available-for-sale securities		71,000	120,000		$ 1,181,000	479,000
Threshold period of value decline in available-for-sale securities to be considered other than temporary impairment					12 months
Threshold percentage of value decline in available-for-sale securities to be considered other than temporary impairment					10.00%
Threshold amount of value decline in available-for-sale securities to be considered other than temporary impairment					$ 10,000
Other than temporary impairment losses on investment securities			$ 0		0	$ 136,000
Debt securities, amortized cost		$ 507,477,000			$ 507,477,000
Obligations of states and political subdivisions
Schedule of Available-for-sale Securities
Other than temporary impairment losses, investments, portion in other comprehensive loss, before tax, including portion attributable to noncontrolling interest, available-for-sale securities	$ 136,000
Other than temporary impairment losses, investments, available-for-sale securities, number of impaired securities | security	1			1
Available-for-sale securities, other than temporary impaired security	$ 2,995,000			$ 2,995,000
Available-for-sale debt securities, other than temporary impairment security, amortized cost basis	$ 3,131,000			$ 3,131,000
Available-for-sale securities, number of positions | security		122			122
Debt securities, amortized cost		$ 204,841,000			$ 204,841,000			288,543,000
Obligations of states and political subdivisions | Less than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		2			2
Obligations of states and political subdivisions | Greater than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		6			6
U.S. Government agencies
Schedule of Available-for-sale Securities
Available-for-sale securities, number of positions | security		21			21
Debt securities, amortized cost		$ 61,253,000			$ 61,253,000			69,005,000
U.S. Government agencies | Less than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		0			0
U.S. Government agencies | Greater than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		2			2
U.S. Government agencies collateralized by residential mortgage obligations
Schedule of Available-for-sale Securities
Available-for-sale securities, number of positions | security		142			142
Debt securities, amortized cost		$ 190,028,000			$ 190,028,000			181,785,000
U.S. Government agencies collateralized by residential mortgage obligations | Less than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		23			23
U.S. Government agencies collateralized by residential mortgage obligations | Greater than 12 months
Schedule of Available-for-sale Securities
Available-for-sale securities in unrealized loss positions, number of positions | security		26			26
Private label mortgage backed securities
Schedule of Available-for-sale Securities
Unrealized gain (loss) of available-for sale securities		$ 599,000			$ 599,000
Available-for-sale securities, number of positions | security		22			22
Available-for-sale securities in unrealized loss positions, number of positions | security		8			8
Debt securities, amortized cost		$ 43,855,000			$ 43,855,000			$ 1,807,000
Private label mortgage backed securities | Below investment grade
Schedule of Available-for-sale Securities
Available-for-sale securities, number of positions | security		10			10
Debt securities, amortized cost		$ 1,431,000			$ 1,431,000
Other equity securities
Schedule of Available-for-sale Securities
Unrealized gain (loss) of available-for sale securities		$ (14,000)			$ (14,000)
Available for sale securities, number of securities | investment		1			1