Goodwill and Intangibles (Details Textuals) - USD ($) $ in Thousands	9 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Goodwill [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	20.00%
Goodwill, Purchase Accounting Adjustments	$ 3,845
Goodwill and Intangibles (Textuals) [Abstract]
Amortization expense for the remainder of 2017	6,200
Amortization expense for 2018	22,400
Amortization expense for 2019	20,600
Amortization expense for 2020	18,800
Amortization expense for 2021	17,300
Amortization expense for 2022	14,900
Measurement period adjustment impact [Domain]
Goodwill [Line Items]
Amortization	156
Customer Relationships [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Purchase Accounting Adjustments	2,636
Trade Names [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Purchase Accounting Adjustments	$ 584
Reliance U.S. business [Domain]
Goodwill [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	149.00%
Other Intangible Assets, Net	$ 15,657
Reliance Canada business [Domain]
Goodwill [Line Items]
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount	13.00%
Other Intangible Assets, Net	$ 80,228
Service Center Based Distribution Segment [Member]
Goodwill [Line Items]
Accumulated goodwill impairment losses	64,794
Goodwill, Purchase Accounting Adjustments	3,220
Fluid Power Businesses [Member]
Goodwill [Line Items]
Accumulated goodwill impairment losses	36,605
Canada Service Centers reporting unit [Member]
Goodwill [Line Items]
Reporting Unit, Amount of Fair Value in Excess of Carrying Amount		$ 8,000
Reporting Unit, Percentage of Fair Value in Excess of Carrying Amount		5.00%
Reporting Unit Carrying Amount		$ 163,000
U.S. Service Centers reporting unit [Domain]
Goodwill [Line Items]
Goodwill, Transfers	$ 2,628