Level 4 Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		6 Months Ended			6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012	Jun. 30, 2013 Accounts Receivable [Member] Credit Concentration Risk [Member]	Dec. 31, 2012 Accounts Receivable [Member] Credit Concentration Risk [Member]	Jun. 30, 2013 6.375% senior notes [Member]	Dec. 31, 2012 6.375% senior notes [Member]
Vendor rebates and allowances	$ 4,000,000		$ 4,000,000		$ 4,100,000
Customer rebates payable	21,200,000		21,200,000		19,700,000
Rental expense	3,700,000	3,600,000	7,300,000	7,200,000
Money market funds, fair value	176,800,000		176,800,000		10,600,000
6.375% senior notes, book value								250,000,000	250,000,000
6.375% senior notes, fair value								$ 253,800,000
Concentration of credit risk						16.00%	14.00%