Business Combinations (Details) - USD ($) $ in Thousands		3 Months Ended
	Dec. 08, 2017	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
Business Combinations
Payment to acquire business, net		$ 47,832
Fair value of assets acquired
Goodwill		$ 69,347		$ 51,705
Minimum | Restricted stock
Business Combinations
Vesting period		3 years
Maximum | Restricted stock
Business Combinations
Vesting period		6 years
MagVAR Acquisition
Business Combinations
Payment to acquire business, net	$ 47,800
Period escrow to be released to seller	12 months
Revenues		$ 600
Net loss		100
Purchase Price
Cash consideration	$ 48,485
Fair value of assets acquired
Current assets	2,304
Property, plant and equipment	13
Intangible assets, net of amortization	28,700
Goodwill	17,642
Total assets acquired	48,659
Fair value of liabilities assumed
Current liabilities	174
Fair value of total assets and liabilities acquired	48,485
Pro forma financial information:
After-tax transaction costs excluded from pro forma earnings		400
Revenues		567,775	$ 370,699
Net income (loss)		499,906	$ (34,889)
MagVAR Acquisition | Prepaid expenses and other
Business Combinations
Restricted cash	$ 6,000
MagVAR Acquisition | Restricted stock
Business Combinations
Restricted stock awards issued	213,904
Vesting period	3 years
MagVAR Acquisition | General and Administrative
Business Combinations
Business acquisition transaction cost		$ 500
MagVAR Acquisition | Minimum
Business Combinations
Estimated useful lives (in years)	5 years
MagVAR Acquisition | Maximum
Business Combinations
Estimated useful lives (in years)	20 years