Long-Term Debt and Borrowings Under Short-Term Credit Agreements - Credit Agreement (Details) (USD $)	9 Months Ended	0 Months Ended							0 Months Ended			0 Months Ended										0 Months Ended
	Sep. 30, 2014	Jun. 06, 2014 Line of Credit Credit Agreement Revolving Credit Facility	Jun. 06, 2014 Line of Credit Credit Agreement Revolving Credit Facility	Dec. 31, 2013 Line of Credit Credit Agreement Revolving Credit Facility	Dec. 31, 2013 Line of Credit Credit Agreement Letter of Credit Sub-Facility	Dec. 31, 2013 Line of Credit Credit Agreement Bridge Loan Graybar Canada	Dec. 31, 2013 Line of Credit Credit Agreement Bridge Loan UNITED STATES	Dec. 31, 2013 Line of Credit Credit Agreement Bridge Loan CANADA	Jun. 06, 2014 Line of Credit Amended Credit Agreement Minimum London Interbank Offered Rate (LIBOR)	Jun. 06, 2014 Line of Credit Amended Credit Agreement Maximum London Interbank Offered Rate (LIBOR)	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility London Interbank Offered Rate (LIBOR)	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility Base Rate	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility Minimum	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility Minimum Base Rate	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility Maximum	Jun. 06, 2014 Line of Credit Amended Credit Agreement Revolving Credit Facility Maximum Base Rate	Jun. 06, 2014 Line of Credit Amended Credit Agreement Letter of Credit Sub-Facility	Jun. 06, 2014 Line of Credit Amended Credit Agreement Bridge Loan Graybar Canada	Jun. 06, 2014 Line of Credit Amended Credit Agreement Bridge Loan UNITED STATES	Jun. 06, 2014 Line of Credit Amended Credit Agreement Bridge Loan CANADA	Jun. 06, 2014 Line of Credit Amended Credit Agreement Letter of Credit Minimum	Jun. 06, 2014 Line of Credit Amended Credit Agreement Letter of Credit Maximum	Sep. 30, 2014 Letter of Credit	Dec. 31, 2013 Letter of Credit	Sep. 30, 2014 Letter of Credit Revolving Credit Facility	Dec. 31, 2013 Letter of Credit Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 550,000,000	$ 500,000,000	$ 50,000,000	$ 100,000,000	$ 50,000,000	$ 20,000,000										$ 50,000,000	$ 100,000,000	$ 50,000,000	$ 20,000,000
Accordion feature, higher borrowing capacity option				200,000,000							300,000,000
Debt Instrument, Term		5 years
Letters of credit outstanding, amount																								$ 6,081,000	$ 6,886,000	$ 356,000	$ 711,000
Commitment fee percentage														0.25%		0.40%						1.00%	1.60%
Description of variable rate basis												LIBOR	base rate loans
Basis spread on variable rate									1.00%	1.60%					0.00%		0.60%
Document Period End Date	Sep. 30, 2014