Equity and Comprehensive Income - Additional Information - Dividends (Detail) - $ / shares	3 Months Ended	6 Months Ended
Feb. 18, 2018	Feb. 12, 2017	Feb. 18, 2018	Feb. 12, 2017
Dividends Payable [Line Items]
Dividends declared	$ 0.50	$ 0.45	$ 1.00	$ 0.90
Dividend Rate
Dividends Payable [Line Items]
Dividends declared	$ 0.50	$ 0.45

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

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

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration