Equity Compensation (Summary of Activity Under Stock Option Plans) (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Options Outstanding
Options outstanding at beginning of period (shares)		33,283
Options exercised (shares)	(17,683)
Options forfeited (shares)	0
Options outstanding at end of period (shares)	15,600	15,600	33,283
Options exercisable at end of period (shares)	15,600	15,600
Options vested at end of period (shares)	15,600	15,600
Weighted- Average Exercise Price Per Share
Options outstanding at beginning of period (in USD per share)		$ 36.40
Options exercised (in USD per share)	$ 39.48
Options forfeited (dollars per share)	0.00
Options outstanding at end of period (in USD per share)	32.91	32.91	$ 36.40
Options exercisable at end of peirod (in USD per share)	32.91	32.91
Options vested at end of period (in USD per share)	$ 32.91	$ 32.91
Weighted-Average Remaining Contractual Life in Years
Weighted-Average Remaining Contractual Life in Year, Options outstanding		2 years 6 months	2 years 2 months
Options exercisable, Weighted-Average Remaining Contractual Life in Years (years)		2 years 6 months
Options vested, Weighted-Average Remaining Contractual Life in Years (years)		2 years 6 months
Aggregate Intrinsic Value
Options outstanding, Aggregate Intrinsic Value	$ 1,225,308	$ 1,225,308	$ 4,177,655
Options exercisable, Aggregate Intrinsic Value	1,225,308	1,225,308
Options vested, Aggregate Intrinsic Value	$ 1,225,308	$ 1,225,308