Summary of Significant Accounting Policies - Shares Used in Computing Basic and Diluted Earnings Per Share (Details) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Denominator (thousands of shares):
Average common shares outstanding for basic computation	173,154	172,760	173,055	172,494
Incremental shares issuable for stock options and awards	2,474	2,361	2,660	2,295
Average common shares outstanding for diluted computation	175,628	175,121	175,715	174,789