Revolving Credit Facility Credit Agreement (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500,000
Combined Letter of Credit Sub-Facility	50,000
US Swing Line Loan Facility	50,000
Canadian Swing Line Loan Facility	20,000
Sublimit for Borrowings by Graybar Canada	100,000
Aggregate Borrowing Commitments	200,000
Letters of Credit Outstanding, Amount	8,922	8,938
Letters of credit, outstanding under revolving credit facility	$ 747	$ 763