Earnings Per Share - Additional Information (Detail)	3 Months Ended	9 Months Ended
Jun. 30, 2016 $ / shares	Jun. 30, 2015 $ / shares	Jun. 30, 2016 Quarter $ / shares	Jun. 30, 2015 $ / shares
Earnings Per Share [Abstract]
Dividend declared \| $ / shares	$ 0.29	$ 0.26	$ 0.87	$ 0.78
Number of quarterly dividends declared \| Quarter			3

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