Capitalization And Short-Term Borrowings (Narrative) (Details)		3 Months Ended	12 Months Ended
	Sep. 18, 2017 USD ($)	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares
Debt Instrument [Line Items]
Issue shares of common stock for the Direct Stock Purchase and Dividend Reinvestment Plan | shares			180,247
Common stock issued for 401(k) plans | shares			103,602
Common stock shares issued due to stock option and SARs exercises | shares			(19,000)
Shares tendered | shares			53,564
Percentage of voting power			10.00%
Percentage of assets or earning power that are sold or transferred		50.00%	50.00%
Equity redemption price per share | $ / shares			$ 0.005
Voting power percentage to redeem rights			75.00%
Rights expiration date			Jul. 31, 2018
Share-Based Payment Expense			$ 10,800,000	$ 4,800,000	$ 2,100,000
Tax benefit related to stock-based compensation expense			4,400,000	1,900,000	900,000
Capitalized stock-based compensation costs			100,000	100,000	100,000
Tax benefit from stock-based compensation exercises and vestings			500,000
Carrying Amount		$ 2,383,681,000	$ 2,383,681,000	2,086,252,000
Percentage of Long-Term Debt issued under 1974 Indenture			4.10%
Net proceeds from issuance of long-term debt			$ 295,151,000	0	444,635,000
Principal amounts of long-term debt maturing in 2018		300,000,000	300,000,000
Principal amounts of long-term debt maturing in 2019		250,000,000	250,000,000
Principal amounts of long-term debt maturing in 2020		0	0
Principal amounts of long-term debt maturing in 2021		0	0
Principal amounts of long-term debt maturing in 2022		500,000,000	500,000,000
Principal amounts of long-term debt maturing after 2022		1,349,000,000	1,349,000,000
Commercial paper, outstanding		0	$ 0	0
Line of Credit Facility, Term Start Date			Oct. 01, 2017
Short-term notes payable outstanding		0	$ 0	0
Debt to capitalization ratio			0.58
Additional borrowing		1,150,000,000	$ 1,150,000,000
Maximum debt increase under existing indenture covenants		$ 126,000,000
Aggregated indebtedness			$ 40,000,000
Preferred stock, shares authorized | shares		10,000,000	10,000,000
Preferred stock par value | $ / shares		$ 1	$ 1
Committed credit facility, outstanding amount		$ 0	$ 0
Stock Options And SARs [Member]
Debt Instrument [Line Items]
Common stock shares issued due to stock option and SARs exercises | shares			45,912
Stock Options [Member]
Debt Instrument [Line Items]
Options, exercises in period, total intrinsic value			$ 300,000	4,100,000	5,100,000
Proceeds from Stock Options Exercised			$ 800,000	$ 8,000,000	$ 5,600,000
Stock Appreciation Rights (SARs) [Member]
Debt Instrument [Line Items]
Number of Shares Granted | shares			0	0	0
Total intrinsic value of SAR's exercised			$ 1,600,000	$ 400,000	$ 2,000,000
Number of Awards Vested | shares			5,000	113,082	157,386
Equity instruments other than options, vested in period, total fair value			$ 100,000	$ 1,200,000	$ 1,700,000
Restricted Share Awards [Member]
Debt Instrument [Line Items]
Number of Shares Granted | shares			0	0	0
Weighted Average Fair Value per Award Granted | $ / shares			$ 0.00
Number of Awards Vested | shares			0
Unrecognized compensation expense		300,000	$ 300,000
Unrecognized compensation expense recognized weighted average period			3 years 1 month 13 days
Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Number of Shares Granted | shares			87,143	101,943	88,899
Weighted Average Fair Value per Award Granted | $ / shares			$ 52.13	$ 35.89	$ 64.04
Number of Awards Vested | shares			80,530
Unrecognized compensation expense		4,700,000	$ 4,700,000
Unrecognized compensation expense recognized weighted average period			2 years 2 months 13 days
Performance Shares [Member]
Debt Instrument [Line Items]
Common stock issued | shares			43,484
Number of Shares Granted | shares			184,148	309,996	107,044
Weighted Average Fair Value per Award Granted | $ / shares			$ 56.39	$ 30.71	$ 65.26
Number of Awards Vested | shares			43,484
Unrecognized compensation expense		10,100,000	$ 10,100,000
Unrecognized compensation expense recognized weighted average period			1 year 8 months 10 days
Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Common stock issued | shares			80,530
3.95% Notes Due September 15, 2027 [Member]
Debt Instrument [Line Items]
Long-term debt, face value	$ 300,000,000
Long-term debt, interest rate	3.95%
Net proceeds from issuance of long-term debt	$ 295,200,000
6.50% Notes Due April 2018 [Member]
Debt Instrument [Line Items]
Long-term debt, face value		$ 300,000,000	$ 300,000,000
Long-term debt, interest rate		6.50%	6.50%
Indenture From 1974 [Member]
Debt Instrument [Line Items]
Carrying Amount		$ 98,700,000	$ 98,700,000
Commercial Paper [Member]
Debt Instrument [Line Items]
Commercial paper available		500,000,000	$ 500,000,000
Board Of Directors [Member]
Debt Instrument [Line Items]
Common stock issued | shares			24,028
Third Amended & Restated Credit Agreement [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		750,000,000.0	$ 750,000,000.0
364-Day Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 500,000,000	$ 500,000,000
Last Day of Fiscal Quarter Through September 30, 2017 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Expiration Date			Sep. 30, 2017
Committed credit facility debt to capitalization ratio			0.675
Last Day of Fiscal Quarter October 1, 2017 through December 5, 2019 [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Expiration Date			Dec. 05, 2019
Committed credit facility debt to capitalization ratio			0.65
2018 [Member] | Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			73,819
2018 [Member] | Performance Shares [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			88,132
2019 [Member] | Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			65,265
2019 [Member] | Performance Shares [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			255,468
2020 [Member] | Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			52,641
2020 [Member] | Performance Shares [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			184,148
2021 [Member] | Restricted Share Awards [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			20,000
2021 [Member] | Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			27,976
2022 [Member] | Non-Performance Based Restricted Stock Units (RSUs) [Member]
Debt Instrument [Line Items]
Non-vested stock-based compensation lapse | shares			13,498