Basis of Presentation, Summary of Significant Accounting Policies and Change in Accounting Principle (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($)
Restricted Cash and Cash Equivalents Items [Line Items]
Number of operating segments | segment	1
Total restricted cash and restricted investments	$ 31,915	$ 40,416
Non-current restricted investments	4,950	4,950
Non-current restricted cash	3,711	1,050
Total non-current restricted cash and restricted investments	8,661	6,000
Current restricted cash and restricted investments	23,254	34,416
Letters of credit for facility leases
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash and restricted investments	3,948	4,852
Collateral with financial institutions
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash and restricted investments	4,950	4,950
Pharmacy benefit management and claims processing services
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash and restricted investments	22,035	30,555
Other
Restricted Cash and Cash Equivalents Items [Line Items]
Total restricted cash and restricted investments	$ 982	$ 59