Capitalized Software Development Costs, Net - Summary of Capitalized Software Development Costs (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Capitalized Computer Software Net [Line Items]
Gross carrying amount	$ 43,629	$ 45,677
Accumulated amortization	(30,187)	(32,784)
Net carrying amount	13,442	12,893
Capitalized Software Development Costs
Capitalized Computer Software Net [Line Items]
Gross carrying amount	$ 43,629	$ 45,677
Amortization period	3 years	3 years
Accumulated amortization	$ (30,187)	$ (32,784)
Net carrying amount	$ 13,442	$ 12,893