Stock-based Compensation (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant under the 2007 Plan (shares)	1,744,000		1,744,000
Option vesting period (years)			4 years
Percentage discount from fair market value for shares purchased under the Employee Stock Purchase Plan			85.00%
Offering period (years)	6 months
Shares available for future issuance under the Employee Stock Purchase Plan (shares)	453,000		453,000
Prior to October 1 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option expiration period (years)			10 years
After October 1 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option expiration period (years)			7 years
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Cliff vesting period			6 months
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Cliff vesting period			1 year
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value of grants	$ 11.26		$ 11.17	$ 9.14
Restricted Stock Units (RSUs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vesting period (years)			2 years
Restricted Stock Units (RSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSU vesting period (years)			4 years
SARS
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period (years)			4 years
Option expiration period (years)			7 years
Total unrecognized stock-based compensation expense	$ 5,600		$ 5,600
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)			3 years 7 months 10 days
SARS | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Cliff vesting period			6 months
SARS | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option Cliff vesting period			1 year
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	10,600		10,600
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)			2 years 8 months 5 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	$ 200		$ 200
Nonvested awards, total compensation cost not yet recognized, period for recognition (years)			4 months
Weighted-average fair value of grants	$ 2.66	$ 2.30	$ 2.66	$ 2.30