Description of Business and Summary of Significant Accounting Policies (Details) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 16, 2014	Jan. 31, 2015 USD ($)	Oct. 31, 2015 USD ($)	Jan. 31, 2017 USD ($) item $ / shares shares	Jan. 31, 2016 USD ($) item	Dec. 31, 2014 USD ($) item shares	Jan. 07, 2016 USD ($)	Dec. 17, 2014 shares
Significant Accounting Policies [Line Items]
Ratio of shares of KLX received for shares of B/E Aerospace	0.5
Accounts receivable, Net
Accounts receivable - trade, allowance for doubtful accounts				$ 13.5	$ 11.3
Inventories
Inventory reserves				$ 59.6	40.4
Goodwill and Intangible Assets, Net
Number of reporting units | item				2
Goodwill impairment charge		$ 0.0	$ 310.4	$ 0.0	310.4	$ 0.0
Intangible assets impairment			177.8		177.8
Property and equipment impairment			$ 152.0
Long-lived assets impairment		$ 0.0		$ 0.0		0.0
Accounting for Stock Based Compensation
Unvested shares, distribution date conversion ratio	1.8139
Qualified employees purchase of stock at a price equal to percentage of closing price				85.00%
Employee Stock Purchase Plan, rights granted				$ 0.3	0.3	$ 0.2
Treasury Stock
Purchase of treasury stock				$ 41.9	12.5
KLX Inc Long Term Incentive Plan
Treasury Stock
Purchase of treasury stock (shares) | shares				35,009
Purchase of treasury stock				$ 1.5
Existing $250.0 Share Repurchase Program
Treasury Stock
Purchase of treasury stock (shares) | shares				982,062
Share repurchase program, authorized amount					$ 250.0		$ 100.0
Purchase of treasury stock				$ 40.5
Repurchased shares, average price per share | $ / shares				$ 41.20
Sales Revenues | Customer Concentration
Concentration of Risk
Concentration risk percentage				10.00%	10.00%	10.00%
Number of customers exceeding the concentration risk percentage threshold | item				0	0	0
Energy Services Group
Goodwill and Intangible Assets, Net
Goodwill impairment charge					$ 310.4
Intangible assets impairment					177.8
Property and equipment impairment					152.0
Long-lived assets impairment					$ 329.8
Minimum
Property and Equipment, Net
Property and equipment, useful lives (years)				1 year
Goodwill and Intangible Assets, Net
Intangible assets, useful lives				5 years
Maximum
Property and Equipment, Net
Property and equipment, useful lives (years)				50 years
Goodwill and Intangible Assets, Net
Intangible assets, useful lives				30 years
Options
Accounting for Stock Based Compensation
Compensation cost						$ 0.0
Stock options granted | shares						0
BE Aerospace, former parent of the Company | Distribution of Stock of Subsidiary to Stockholders to Effect Spin-Off
Significant Accounting Policies [Line Items]
Shares Issued | shares								52,500,000
Ratio of shares of KLX received for shares of B/E Aerospace	0.5