Equity (Schedule of Common Stock Reserved for Future Issuances) (Details) - shares	Dec. 31, 2017	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise of outstanding stock options (in shares)	309,598	326,798
Purchases under the employee stock purchase plan (in shares)	911,071
Issuance of stock-based awards under the Equity Plans (in shares)	1,882,779
Purchases under the officer and director share purchase plan (in shares)	88,741
Total reserved (in shares)	4,952,826
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested stock units (in shares)	955,009	778,084
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested stock units (in shares)	402,814	328,708
Unvested performance stock units (in shares)	805,628