SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Supplier shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2013 USD ($) shares
Significant Accounting Policies [Line Items]
Percentage of parent and wholly-owned subsidiaries assets and liabilities included in financial statements (in Percent)	100.00%
Other-than-temporary impairments on investments	$ 0	$ 0	$ 0
Reserve for excess and obsolete inventory	1,253	460
Net book value of capitalized software	15,022	13,162
Reductions to remaining useful lives or write-downs of long-lived assets	0
Revenue from shipping and handling charges	$ 2,561	2,013	2,000
Charge recorded to settle a contract dispute			5,000
Number of suppliers providing volume purchase rebates | Supplier	1
Reduced cost of revenue, rebate earned	$ 698	883	1,068
Amount of rebate receivable recorded in balance sheet	0	360
Media expense	$ 104,621	89,304	$ 77,396
Period after initial mailing during which benefits are expected to be received (in Duration)	40 days
Future advertisements and promotions, costs prepaid	$ 3,311	1,958
Tenant improvement allowance, included in consolidated balance sheets	$ 2,266	$ 2,611
Common stock equivalents excluded from weighted average shares outstanding for diluted income per common share purposes (in Shares) | shares	229	377	786
Payment for income taxes	$ 13,508	$ 7,118	$ 2,842
Payment for interest	182	168	116
Non-cash capital additions	670	483	$ 42
Other Accrued Expenses And Current liabilities [Member]
Significant Accounting Policies [Line Items]
Tenant improvement allowance, included in consolidated balance sheets	345	345
Non-current Liabilities [Member]
Significant Accounting Policies [Line Items]
Tenant improvement allowance, included in consolidated balance sheets	$ 1,921	$ 2,266
Inventory Purchases [Member] | Major Supplier 1 [Member]
Significant Accounting Policies [Line Items]
Percent concentration risk (in Percent)	19.00%	14.00%	12.00%
Inventory Purchases [Member] | Major Supplier 2 [Member]
Significant Accounting Policies [Line Items]
Percent concentration risk (in Percent)	17.00%	17.00%	14.00%
Fulfillment Cost [Member] | Third Party Fulfillment Provider Concentration [Member]
Significant Accounting Policies [Line Items]
Percent concentration risk (in Percent)	100.00%
Minimum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life (in Duration)	2 years
Minimum [Member] | Shipping Costs [Member] | Shipping Provider [Member]
Significant Accounting Policies [Line Items]
Percent concentration risk (in Percent)	96.00%
Minimum [Member] | Internal-Use Software and Website Development [Member]
Significant Accounting Policies [Line Items]
Estimated useful life (in Duration)	2 years
Maximum [Member]
Significant Accounting Policies [Line Items]
Estimated useful life (in Duration)	7 years
Maximum [Member] | Internal-Use Software and Website Development [Member]
Significant Accounting Policies [Line Items]
Estimated useful life (in Duration)	5 years