Liability for Unpaid Claims - Short-duration Contracts, Claims Development (Details) $ in Thousands	Dec. 31, 2016 USD ($) claim	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Claims Development [Line Items]
Incurred claims	$ 549,239
Total of incurred-but-not-reported liabilities plus expected development on reported claims	26,721
Incurred claims	26,721
2012
Claims Development [Line Items]
Incurred claims	83,906	$ 83,906	$ 83,928	$ 83,965	$ 84,975
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	1,357,000
2013
Claims Development [Line Items]
Incurred claims	$ 83,119	83,151	82,644	84,111
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 0
Cumulative number of reported claims | claim	1,337,000
2014
Claims Development [Line Items]
Incurred claims	$ 99,810	99,876	101,407
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 19
Cumulative number of reported claims | claim	1,600,000
2015
Claims Development [Line Items]
Incurred claims	$ 141,460	141,667
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 478
Cumulative number of reported claims | claim	2,222,000
2016
Claims Development [Line Items]
Incurred claims	$ 140,944
Total of incurred-but-not-reported liabilities plus expected development on reported claims	$ 26,224
Cumulative number of reported claims | claim	1,863,000
Health Insurance Product Line
Claims Development [Line Items]
Cumulative paid claims	$ 522,518
Short-duration claim liability as of December 31, 2016	26,721
Incurred claims	549,239
Health Insurance Product Line | 2012
Claims Development [Line Items]
Cumulative paid claims	83,906	83,906	83,919	83,766	$ 68,742
Health Insurance Product Line | 2013
Claims Development [Line Items]
Cumulative paid claims	83,119	83,131	82,408	$ 68,159
Health Insurance Product Line | 2014
Claims Development [Line Items]
Cumulative paid claims	99,791	99,545	$ 81,054
Health Insurance Product Line | 2015
Claims Development [Line Items]
Cumulative paid claims	140,982	$ 115,922
Health Insurance Product Line | 2016
Claims Development [Line Items]
Cumulative paid claims	$ 114,720