Quarterly report pursuant to Section 13 or 15(d)

Debt - Interest Rate Contracts (Details)

v3.7.0.1
Debt - Interest Rate Contracts (Details) - Cash Flow Hedging - Designated as Hedging Instrument - Interest rate swap contracts - USD ($)
$ in Thousands
6 Months Ended 12 Months Ended
Mar. 31, 2017
Sep. 30, 2016
Derivative [Line Items]    
Pay fixed swaps - notional amount $ 371,875 $ 403,125
Net unrealized gain (loss) $ 4,438 $ (5,834)
Weighted-average maturity period (years) 3 years 7 months 6 days 3 years 10 months 25 days
Weighted-average received rate (as a percent) 0.98% 0.53%
Weighted-average pay rate (as a percent) 1.27% 1.26%