Summary of Significant Accounting Policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) customer	Dec. 31, 2014 USD ($) customer	Dec. 31, 2013 USD ($) customer
Schedule of Accounting Policies [Line Items]
Investments in certificates of deposit	$ 12,000	$ 11,400
Certificates of deposit interest rate, lower range	0.25%
Certificates of deposit interest rate, upper range	0.90%
Investments held to maturity	$ 17,483	15,987
Research and development costs	7,500	6,300	$ 5,200
Advertising expense	1,200	1,000	900
Shipping and handling fees	9,600	8,500	7,900
Payments to representatives	$ 55,400	$ 59,700	$ 63,000
Extended product warranties, minimum length	6 months
Extended product warranties, maximum length	10 years
Foreign Sales Revenue, Net [Member]
Schedule of Accounting Policies [Line Items]
Concentration risk, percentage	4.00%	6.00%	5.00%
Sales Revenue, Net [Member]
Schedule of Accounting Policies [Line Items]
Number of major customers | customer	1	0	0
Accounting for More Than 5% of Accounts Receivable
Schedule of Accounting Policies [Line Items]
Number of major customers	0	0
Concentration risk, percentage	5.00%	5.00%
Minimum
Schedule of Accounting Policies [Line Items]
Certificates of deposit maturity dates	1 month
Investments maturity date	1 month
Maximum
Schedule of Accounting Policies [Line Items]
Certificates of deposit maturity dates	15 months
Investments maturity date	15 months