Stock-Based Compensation and Directors Stock Purchase Plan (Summary Of SAR Activity) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Stock Appreciation Rights, Shares [Roll Forward]
Outstanding, Shares, Beginning Balance | shares	1,237,804
Granted, Shares | shares	177,001
Forfeited, Shares | shares	(17,529)
Expired, Shares | shares	(607)
Exercised, Shares | shares	(330,231)
Outstanding, Shares, Ending Balance | shares	1,066,438
Exercisable, Shares, Ending Balance | shares	561,527
Stock Appreciation Rights, Weighted Average Exercise Price [Roll Forward]
Outstanding, Weighted Average Exercise Price, Beginning Balance | $ / shares	$ 35.36
Granted, Weighted Average Exercise Price | $ / shares	55.63
Forfeited, Weighted Average Exercise Price | $ / shares	45.82
Expired, Weighted Average Exercise Price | $ / shares	43.14
Exercised, Weighted Average Exercise Price | $ / shares	29.96
Outstanding, Weighted Average Exercise Price, Ending Balance | $ / shares	40.22
Exercisable, Weighted Average Exercise Price, Ending Balance | $ / shares	$ 34.57
Outstanding, Weighted Average Remaining Contractual Term (in years)	6 years 8 months
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding | $	$ 17,218
Exercisable, Weighted Average Remaining Contractual Term (in years)	5 years 7 months
Exercisable, Aggregate Intrinsic Value, Ending Balance | $	$ 12,239