Stock Based Compensation, Stock Option Activity (Details) - Stock Options [Member] - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Options outstanding [Roll Forward]
Outstanding at beginning of period (in shares)	20,265	24,669
Exercised (in shares)	(2,631)	(3,398)
Expired (in shares)	0	(1,006)
Outstanding at end of period (in shares)	17,634	20,265
Exercisable at end of period (in shares)	17,634	20,265
Weighted average exercise price [Roll forward]
Outstanding at beginning of period (in dollars per share)	$ 11.42	$ 12.17
Exercised (in dollars per share)	12.55	14.97
Expired (in dollars per share)	0.00	17.88
Outstanding at end of period (in dollars per share)	11.25	11.42
Exercisable at end of period (in dollars per share)	$ 11.25	$ 11.42