Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)	9 Months Ended
	Sep. 30, 2018 $ / shares shares
Nonvested Share Awards [Roll Forward]
Nonvested, Shares, Beginning Balance | shares	1,254,518
Granted, Shares | shares	246,778
Vested, Shares | shares	(348,940)
Forfeited, Shares | shares	(23,772)
Nonvested, Shares, Ending Balance | shares	1,128,584
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 38.67
Granted , Weighted Average Grant Date Fair Value | $ / shares	60.08
Vested , Weighted Average Grant Date Fair Value | $ / shares	32.32
Forfeited , Weighted Average Grant Date Fair Value | $ / shares	46.35
Nonvested , Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 45.15