Share-Based Compensation Plans - Company's restricted stock award activity (Details) - Restricted Stock [Member] $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of Restricted Stock, Non-vested beginning of year | shares	61,480
Shares of Restricted Stock, Issued | shares	600
Shares of Restricted Stock, Vested | shares	0
Shares of Restricted Stock, Forfeited | shares	0
Shares of Restricted Stock, Non-vested end of year | shares	62,080
Weighted Average Grant Date Fair Value, Non-vested beginning of year (in dollars per share) | $ / shares	$ 30.74
Weighted Average Grant Date Fair Value, Issued (in dollars per share) | $ / shares	28.77
Weighted Average Grant Date Fair Value, Vested (in dollars per share) | $ / shares	0
Weighted Average Grant Date Fair Value, Forfeited (in dollars per share) | $ / shares	0
Weighted Average Grant Date Fair Value, Non-vested end of year (in dollars per share) | $ / shares	$ 30.72
Weighted Average Remaining Contractual Term (Years)	2 years 2 months 12 days
Aggregate Intrinsic Value | $	$ 1,658,000