Deferred Costs	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Deferred Costs	Deferred CostsDeferred costs, which primarily consist of costs to obtain contracts with customers, were $13.3 million as of September 30, 2018. Amortization expense for the deferred costs was $2.5 million and $6.9 million for the three and nine months ended September 30, 2018, respectively. There was no significant impairment loss in relation to the costs capitalized for the periods presented.