Borrowings Under Short-Term Credit Agreements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Sep. 28, 2011	Sep. 27, 2011
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 500,000	$ 200,000
Sublimit for Borrowings by Graybar Canada			100,000
Aggregate Borrowing Commitments			200,000
Credit agreement commitment fee percentage	0.35%	0.35%
Short-term Debt [Abstract]
Letters of credit outstanding	8,938
Letters of credit, outstanding under revolving credit facility	763
Short-term borrowings	71,116	42,562
Short-term borrowings outstanding, daily average	67,000	52,000
Short-term borrowings weighted average interest rate	1.88%	1.86%
Total debt, weighted average interest rate	1.66%
Line of credit, remaining borrowing capacity	428,884	457,438
Long-Term debt, fixed rate debt carrying amount in excess of fair value	215	925
Minimum
Short-term Debt [Abstract]
Short-term borrowings oustanding	35,105	13,800
Maximum
Short-term Debt [Abstract]
Short-term borrowings oustanding	111,032	91,548
Lender's Base Rate Plus Market Spread | Credit Agreement
Line of Credit Facility [Line Items]
Description of variable rate basis	base rate loans
Letter of Credit
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			50,000
Letter of Credit | Minimum
Line of Credit Facility [Line Items]
Credit agreement commitment fee percentage	1.05%
Letter of Credit | Maximum
Line of Credit Facility [Line Items]
Credit agreement commitment fee percentage	1.65%
Line of credit | Minimum
Line of Credit Facility [Line Items]
Credit agreement commitment fee percentage	0.20%
Line of credit | Maximum
Line of Credit Facility [Line Items]
Credit agreement commitment fee percentage	0.35%
Line of credit | Lender's Base Rate Plus Market Spread | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.05%
Line of credit | Lender's Base Rate Plus Market Spread | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.65%
Line of credit | Libor Plus Market-rate Spreads
Line of Credit Facility [Line Items]
Description of variable rate basis	LIBOR
Line of credit | Libor Plus Market-rate Spreads | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.05%
Line of credit | Libor Plus Market-rate Spreads | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.65%
UNITED STATES | US Swing line loan facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			50,000
CANADA | Canadian Swing line loan facility
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 20,000