Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)	9 Months Ended
	Sep. 30, 2017 $ / shares shares
Nonvested Share Awards [Roll Forward]
Nonvested, Shares, Beginning Balance | shares	1,392,451
Granted, Shares | shares	242,244
Vested, Shares | shares	(403,586)
Forfeited, Shares | shares	(20,250)
Nonvested, Shares, Ending Balance | shares	1,210,859
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 34.67
Granted , Weighted Average Grant Date Fair Value | $ / shares	57.31
Vested , Weighted Average Grant Date Fair Value | $ / shares	30.87
Forfeited , Weighted Average Grant Date Fair Value | $ / shares	40.72
Nonvested , Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 40.36