Organization and Description of Business - Credit Risk (Details) - item	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Concentrations of Credit Risk and Other Risks and Uncertainties
Number of major financial institutions with which the company's cash and cash equivalents are deposited	1		1
Revenue | Revenue concentration risk
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	43.00%	42.00%	42.00%	40.00%
Revenue | Revenue concentration risk | Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	30.00%	28.00%	30.00%	26.00%
Revenue | Revenue concentration risk | United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)	13.00%	14.00%	12.00%	14.00%
Accounts receivable | Gross receivables concentration risk | Medicare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)			42.00%		31.00%
Accounts receivable | Gross receivables concentration risk | United Healthcare
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)			17.00%		25.00%
Accounts receivable | Gross receivables concentration risk | Aetna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)			14.00%		23.00%
Accounts receivable | Gross receivables concentration risk | Cigna
Concentrations of Credit Risk and Other Risks and Uncertainties
Concentrations of credit risk (as a percent)			14.00%		8.00%