Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Provisions for doubtful accounts	$ 2,928	$ 1,577	$ 1,474
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	8,000	6,800	5,700
Provisions for doubtful accounts	2,928	1,577	1,474
Deductions - returns and write-offs	2,228	377	374
Balance at end of year	$ 8,700	$ 8,000	$ 6,800