Business Segments - Reconciliation of Health Premium Included in the segment Analysis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Health premium	$ 307,791	$ 290,584	$ 637,654	$ 604,455
Health premium earned per segment, Change %			5.00%
Medicare Part D [Member]
Segment Reporting Information [Line Items]
Health premium			167,990	149,809
Health premium earned per segment, Change %			12.00%
Other Health [Member]
Segment Reporting Information [Line Items]
Health premium			434,533	439,751
Health premium earned per segment, Change %			(1.00%)
Part D risk sharing adjustment [Member]
Segment Reporting Information [Line Items]
Health premium			$ 35,131	$ 14,895
Health premium earned per segment, Change %			136.00%