Share-Based Compensation Plan - Stock options outstanding activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Shares [Roll Forward]
Outstanding at beginning of year (in shares)	30,012	30,012	58,513
Granted (in shares)	0	0	0
Exercised (in shares)	(6,650)	0	(25,501)
Forfeited or expired (in shares)	0	0	(3,000)
Outstanding at end of period (in shares)	23,362	30,012	30,012
Options exercisable at year end (in shares)	23,362	30,012	30,012
Weighted Average Exercise Price [Roll Forward]
Outstanding at beginning of year (in dollars per share)	$ 14.00	$ 14.00	$ 15.30
Granted (in dollars per share)	0.00	0.00	0.00
Exercised (in dollars per share)	14.00	0.00	14.00
Forfeited or expired (in dollars per share)	0.00	0.00	39.40
Outstanding at end of period (in dollars per share)	14.00	14.00	14.00
Options exercisable at year end (in dollars per share)	$ 14.00	$ 14.00	$ 14.00