Stock Options - Schedule of Options Outstanding (Details) - $ / shares		3 Months Ended
	Aug. 27, 2015	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Options, Outstanding
Outstanding, beginning of year (in shares)		263,700	93,500
Granted (in shares)	38,750	160,000	25,000
Exercised (in shares)		0	0
Forfeited (in shares)	(15,250)	0	0
Expired (in shares)		0	0
Outstanding, end of period (in shares)	23,500	423,700	118,500
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding, weighted average exercise price (in dollars per share)		$ 43.94	$ 43.91	$ 45.12	$ 43.59
Granted (in dollars per share)	$ 42.03	42.01	45.11
Exercised (in dollars per share)		0.00	0.00
Forfeited (in dollars per share)		0.00	0.00
Expired (in dollars per share)		$ 0.00	$ 0.00
Exercisable, end of period (in shares)		0	0
Exercisable, end of period (in dollars per share)		$ 0.00	$ 0.00