Loans and Allowance for Loan Losses - Loan Summary (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 865,421,000	$ 813,376,000
Less: Allowance for loan losses	(5,498,000)	(5,105,000)	$ (4,354,000)
Loans, net	859,922,516	808,271,003
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	25,211,000	27,193,000
Less: Allowance for loan losses	0	0
Loans, net	25,211,000	27,193,000
All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	840,210,000	786,183,000
Less: Allowance for loan losses	(5,498,000)	(5,105,000)
Loans, net	834,712,000	781,078,000
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	445,189,000	415,208,000
Less: Allowance for loan losses	(2,489,000)	(2,369,000)	(1,906,000)
Commercial Real Estate [Member] | Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	14,417,000	14,943,000
Commercial Real Estate [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	430,772,000	400,265,000
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	206,667,000	187,802,000
Less: Allowance for loan losses	(1,653,000)	(1,382,000)	(1,015,000)
Consumer Real Estate [Member] | Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	8,071,000	9,004,000
Consumer Real Estate [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	198,596,000	178,798,000
Construction and Land Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	101,156,000	117,869,000
Less: Allowance for loan losses	(609,000)	(717,000)	(627,000)
Construction and Land Development [Member] | Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,474,000	1,678,000
Construction and Land Development [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	99,682,000	116,191,000
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	105,233,000	85,022,000
Less: Allowance for loan losses	(644,000)	(520,000)	(777,000)
Commercial and Industrial [Member] | Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	1,249,000	1,568,000
Commercial and Industrial [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	103,984,000	83,454,000
Consumer and Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	7,176,000	7,475,000
Less: Allowance for loan losses	(103,000)	(117,000)	$ (29,000)
Consumer and Other [Member] | Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	0	0
Consumer and Other [Member] | All Other Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans	$ 7,176,000	$ 7,475,000