Long-Lived Assets - Summary of Aggregate Amortization Related to Client Contract Costs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Capitalized Contract Cost [Line Items]
Total client contract costs, aggregate amortization	$ 5,478
Client contract incentives
Capitalized Contract Cost [Line Items]
Total client contract costs, aggregate amortization	2,727
Capitalized costs
Capitalized Contract Cost [Line Items]
Total client contract costs, aggregate amortization	2,395
Capitalized commission fees
Capitalized Contract Cost [Line Items]
Total client contract costs, aggregate amortization	$ 356