Business Segments - Reconciliation of Health Premium Included in the Segment Analysis (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Premium per segment analysis:
Health premium	$ 280,744	$ 293,879	$ 913,001	$ 931,533
Health premium, % Change			(2.00%)
Medicare Part D premium [Member]
Premium per segment analysis:
Health premium			$ 232,102	258,243
Health premium, % Change			(10.00%)
Other health premium [Member]
Premium per segment analysis:
Health premium			$ 690,221	644,758
Health premium, % Change			7.00%
Part D risk sharing adjustment [Member]
Premium per segment analysis:
Health premium			$ (9,322)	$ 28,532
Health premium, % Change			(133.00%)