Income Taxes - Net Deferred Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Net operating loss carry-forward	$ 48,766	$ 25,100
Stock-based compensation	9,071	7,668
Chargeback reserves	14,173	17,802
Reserve for product returns	8,012	9,479
Inventory valuation reserve	9,688	10,207
Long-term debt	2,226	3,084
Interest greater than 30% of EBITDA	13,930	0
Other	16,444	10,806
Total deferred tax assets	122,310	84,146
Valuation allowance	(71,157)	(10,531)	$ (9,900)
Net deferred tax assets	51,153	73,615
Deferred tax liabilities:
Prepaid expenses	(2,137)	(1,709)
Depreciation & amortization – tax over book	(49,547)	(108,788)
Other	(35)	0
Total deferred tax liabilities	(51,719)	(110,497)
Net deferred income tax liability	$ (566)	$ (36,882)