Commitments and Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018	Sep. 30, 2017
Operating Leased Assets [Line Items]
Rent expense	$ 5,354	$ 4,817	$ 10,916	$ 9,754
Letters of credit outstanding, amount			11,777
Letter of Credit
Operating Leased Assets [Line Items]
Letters of credit outstanding, amount	14,541		11,777
Surety Bond [Member]
Operating Leased Assets [Line Items]
Surety bonds	133,555		123,427
Siemens [Member]
Operating Leased Assets [Line Items]
Letters of credit outstanding, amount	0		857
Siemens [Member] | Surety Bond [Member]
Operating Leased Assets [Line Items]
Surety bonds	$ 2,429		$ 2,469
Minimum
Operating Leased Assets [Line Items]
Lessor, operating lease, term of contract	5 years
Minimum | Surety Bond [Member]
Operating Leased Assets [Line Items]
Financial instruments, commitments, expiration period	12 months
Maximum
Operating Leased Assets [Line Items]
Lessor, operating lease, term of contract	20 years
Maximum | Surety Bond [Member]
Operating Leased Assets [Line Items]
Financial instruments, commitments, expiration period	10 years