Receivables and Allowance for Doubtful Accounts Receivables and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Receivables [Line Items]
Accounts Receivable, before Allowance for Credit Loss	$ 89,724	$ 74,528
Receivables, net of allowance for doubtful accounts of $5,601 and $4,883 in 2019 and 2018, respectively	84,123	69,645
Changes in allowance for doubtful accounts [Roll Forward]
Bad debt expense	15,077	14,610	$ 15,702
Accounts written off	(14,359)	(13,894)	(15,128)
Allowance for doubtful accounts	(5,601)	(4,883)	$ (4,167)	$ (3,593)
Installment sales receivable [Member]
Receivables [Line Items]
Accounts Receivable, before Allowance for Credit Loss	56,370	54,746
Changes in allowance for doubtful accounts [Roll Forward]
Allowance for doubtful accounts	(4,100)	(3,600)
Trade and notes receivables [Member]
Receivables [Line Items]
Accounts Receivable, before Allowance for Credit Loss	33,354	19,782
Changes in allowance for doubtful accounts [Roll Forward]
Allowance for doubtful accounts	$ (1,500)	$ (1,300)