Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 88,145	$ 110,121
Less allowance for doubtful accounts	(3,590)	(2,574)
Accounts receivable, net	84,555	107,547
Trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	52,565	58,067
Unpaid amounts for benefit services
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, gross	$ 35,580	$ 52,054