Stock-Based Compensation and Directors Stock Purchase Plan (Summary Of The Status Of Nonvested Share Awards) (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Nonvested Share Awards [Roll Forward]
Nonvested, share awards, beginning balance | shares	1,317,092
Granted, Shares | shares	268,658
Vested, Shares | shares	(376,489)
Forfeited, Shares | shares	(28,321)
Canceled, Shares | shares	0
Nonvested, share awards, ending balance | shares	1,180,940
Nonvested Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 36.82
Granted, Weighted Average Grant Date Fair Value | $ / shares	57.28
Vested, Weighted Average Grant Date Fair Value | $ / shares	30.73
Forfeited, Weighted Average Grant Date Fair Value | $ / shares	44.12
Canceled, Weighted Average Grant Date Fair Value | $ / shares	0.00
Nonvested , Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 43.24