Debt - Credit Agreement (Details) (USD $)	3 Months Ended	0 Months Ended
	Mar. 31, 2015	Jun. 06, 2014	Dec. 31, 2014
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 454,180,000		$ 483,658,000
Commitment fee percentage	0.40%
Line of Credit | Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt Instrument, Term		5 years
Maximum borrowing capacity		550,000,000
Accordion feature, higher borrowing capacity option		300,000,000
Line of Credit | Credit Agreement | Letter of Credit Sub-Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		50,000,000
Line of Credit | Credit Agreement | Bridge Loan | Graybar Canada
Line of Credit Facility [Line Items]
Maximum borrowing capacity		100,000,000
Line of Credit | Credit Agreement | Bridge Loan | UNITED STATES
Line of Credit Facility [Line Items]
Maximum borrowing capacity		50,000,000
Line of Credit | Credit Agreement | Bridge Loan | CANADA
Line of Credit Facility [Line Items]
Maximum borrowing capacity		20,000,000
Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount	5,290,000		5,725,000
Letter of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Letters of credit outstanding, amount	$ 0		$ 0