Earnings per Share Reconciliation of Weighted Average Common Shares Outstanding for Purposes of Calculating Basic and Diluted Earnings Per Share (Detail) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Weighted average common shares outstanding used in computing basic earnings per share	67,387	66,646	67,255	66,499
Dilutive common stock options and restricted stock units	1,027	859	0	884
Weighted average common shares outstanding for purposes of computing diluted earnings per share	68,414	67,505	67,255	67,383