Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Sep. 30, 2014 Accounts Receivable [Member] Credit Concentration Risk [Member]	Dec. 31, 2013 Accounts Receivable [Member] Credit Concentration Risk [Member]	Sep. 30, 2014 Senior Notes Due 2020 [Member] Senior notes [Member]	Dec. 31, 2013 Senior Notes Due 2020 [Member] Senior notes [Member]
Vendor rebates and allowances	$ 4,800,000		$ 4,800,000		$ 4,700,000
Customer Rebates and Allowances	28,000,000		28,000,000		24,200,000
Rental expense	4,300,000	3,800,000	12,900,000	11,100,000
Money market funds, fair value	130,400,000		130,400,000		85,800,000
6.375% senior notes, book value	301,466,000		301,466,000		301,613,000			299,990,000	299,990,000
6.375% senior notes, fair value								$ 312,000,000
Concentration of credit risk						13.00%	13.00%
Threshold for accounts receivable from single customer, percentage						10.00%