Basis of Presentation (Summary of Stock Options Outstanding) (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Shares
Outstanding at beginning of period (in shares)	6,500	26,400
Granted (in shares)	0	0
Exercised (in shares)	(6,500)	(5,500)
Forfeited (in shares)	0	0
Outstanding at end of period (in shares)	0	20,900
Options exercisable at end of period (in shares)	0	20,900
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 18.60	$ 18.60
Granted (in dollars per share)	0.00	0.00
Exercised (in dollars per share)	18.60	18.60
Forfeited (in dollars per share)	0.00	0.00
Outstanding at end of period (in dollars per share)	0.00	18.60
Options exercisable at end of period (in dollars per share)	$ 0.00	$ 18.60