Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017
Operating Leased Assets [Line Items]
Rent expense	$ 4,817	$ 4,360	$ 9,754	$ 8,833
Letters of credit outstanding, amount	17,274		17,274		$ 20,663
Equipment [Member]
Operating Leased Assets [Line Items]
Capital leased assets, gross	48,146		48,146		43,727
Capital leases, carrying value	30,613		30,613		30,302
Letter of Credit [Member]
Operating Leased Assets [Line Items]
Letters of credit outstanding, amount	20,612		20,612		6,706
Surety Bond [Member]
Operating Leased Assets [Line Items]
Surety bonds	87,849		87,849		98,820
Siemens [Member]
Operating Leased Assets [Line Items]
Letters of credit outstanding, amount	901		901		922
Siemens [Member] | Surety Bond [Member]
Operating Leased Assets [Line Items]
Surety bonds	$ 12,970		$ 12,970		$ 5,570
Minimum [Member]
Operating Leased Assets [Line Items]
Lessor, operating lease, term of contract			5 years
Minimum [Member] | Surety Bond [Member]
Operating Leased Assets [Line Items]
Financial instruments, commitments, expiration period			12 months
Maximum [Member]
Operating Leased Assets [Line Items]
Lessor, operating lease, term of contract			20 years
Maximum [Member] | Surety Bond [Member]
Operating Leased Assets [Line Items]
Financial instruments, commitments, expiration period			10 years