Debt (Narrative) (Details) (USD $)	0 Months Ended	6 Months Ended
	May 14, 2012	Mar. 31, 2013	Sep. 30, 2012	Mar. 31, 2012	Sep. 30, 2011
Debt Instrument [Line Items]
Revolving credit facility		$ 330,000,000
Available to borrow under the credit facility		260,000,000
Option amount to increase credit facility		250,000,000
Cash on hand		35,880,000	30,215,000	27,071,000	34,158,000
Outstanding borrowings under the credit facility		176,000,000
Outstanding letters of credit		13,900,000
Number of lenders	8
Percentage of foreign subsidiaries' share equity		65.00%
Minimum [Member]
Debt Instrument [Line Items]
Incremental term loan		25,000,000
Credit facility fees		0.175%
Maximum [Member]
Debt Instrument [Line Items]
Incremental term loan		250,000,000
Credit facility fees		0.35%
JPMorgan Chase Bank N.A. [Member]
Debt Instrument [Line Items]
Revolving credit facility	450,000,000
Revolving credit facility period	5 years