Description of Business and Significant Accounting Policies - Narrative (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) segment reporting_unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Number of reporting units | reporting_unit	1
Number of reportable segments | segment	1
Accumulated deficit	$ (219,000,000)	$ (266,000,000)
Advance collection	95,000,000	23,000,000
Maximum reimbursement per claim occurrence	$ 1,000,000
Plan years to be settled	10 years
Prepaid Insurance	$ 39,000,000	33,000,000
Weighted-average rate used in discounting the lease liabilities	4.40%
Accounts receivable allowance for doubtful accounts	$ 0	1,000,000
Impairment of goodwill	0	0	$ 0
Impairment of finite-lived intangible assets	0	0	0
Advertising costs	18,000,000	17,000,000	8,000,000
Bad debt expense net of recoveries	$ 1,000,000	1,000,000	$ 1,000,000
Minimum
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of intangible assets	2 years
Minimum | Software Development
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of intangible assets	3 years
Minimum | Software And Office Equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of property and equipment	3 years
Minimum | Furniture, fixtures, and equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of property and equipment	5 years
Maximum
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of intangible assets	10 years
Maximum | Software Development
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of intangible assets	5 years
Maximum | Software And Office Equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of property and equipment	5 years
Maximum | Furniture, fixtures, and equipment
Summary Of Significant Accounting Policy [Line Items]
Estimated useful life of property and equipment	7 years
Non-US | Geographic Concentration Risk | Revenue
Summary Of Significant Accounting Policy [Line Items]
Concentration risk percentage	1.00%
Health Care
Summary Of Significant Accounting Policy [Line Items]
Prepaid Insurance	$ 52,000,000	$ 50,000,000
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Summary Of Significant Accounting Policy [Line Items]
Accumulated deficit				$ 2,000,000