Schedule II - Valuation and Qualifying Accounts (Tables)

12 Months Ended

Dec. 31, 2017

Valuation and Qualifying Accounts [Abstract]

Valuation and qualifying accounts

Description	Balance at Beginning of Period		Additions - Charged to Costs and Expenses		Additions - Charged to Other Accounts - Describe		Deductions -  Describe			Balance at End of Period
Sales and returns allowances:
For the year ended December 31, 2017	$	9,595	$	1,347	$	—	$	—		$	10,942
For the year ended December 31, 2016	7,978		1,617		—		—			9,595
For the year ended December 31, 2015	$	6,855	$	1,123	$	—	$	—		$	7,978
Allowance for doubtful accounts:
For the year ended December 31, 2017	$	12,040	$	8,598	$	—	$	7,921	(1)	$	12,717
For the year ended December 31, 2016	9,637		9,587		—		7,184		(1)	12,040
For the year ended December 31, 2015	$	8,713	$	7,119	$	—	$	6,195	(1)	$	9,637

⁽¹⁾  Uncollectable accounts written off.