Revenue Recognition - Narrative (Details)	3 Months Ended	6 Months Ended
	Jun. 30, 2019 segment	Jun. 30, 2019 segment product_category
Disaggregation of Revenue [Line Items]
Refund period		90 days
Number of principal categories of products | product_category		6
Number of business segments | segment	4	4
Maximum
Disaggregation of Revenue [Line Items]
Contract with customer, contract term		1 year