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Dividends (Narrative) (Details) - $ / shares			3 Months Ended		6 Months Ended
	Jan. 18, 2018	Oct. 19, 2017	Mar. 31, 2018	Mar. 25, 2017	Mar. 31, 2018	Mar. 25, 2017
Class A Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock			$ 0.165	$ 0.165	$ 0.33	$ 0.33
Class B Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock			$ 0.150	$ 0.150	$ 0.30	$ 0.30
Dividend 1 [Member]
Dividends Payable [Line Items]
Dividend payment date					Oct. 19, 2017
Dividend record date					Oct. 12, 2017
Dividend 1 [Member] | Class A Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock		$ 0.165
Dividend 1 [Member] | Class B Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock		$ 0.15
Dividend 2 [Member]
Dividends Payable [Line Items]
Dividend payment date					Jan. 18, 2018
Dividend record date					Jan. 11, 2018
Dividend 2 [Member] | Class A Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock	$ 0.165
Dividend 2 [Member] | Class B Common Stock [Member]
Dividends Payable [Line Items]
Cash dividends per share of common stock	$ 0.15

X

- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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