Business Segments - Reconciliation of Health Premium Included in the segment Analysis (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	[1]	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Health premium	$ 315,492	$ 307,791		$ 632,257	$ 637,654	[1]
Health premium earned per segment, Change %				(1.00%)
Medicare Part D [Member]
Segment Reporting Information [Line Items]
Health premium				$ 154,705	167,990
Health premium earned per segment, Change %				(8.00%)
Other Health [Member]
Segment Reporting Information [Line Items]
Health premium				$ 461,082	434,533
Health premium earned per segment, Change %				6.00%
Part D risk sharing adjustment [Member]
Segment Reporting Information [Line Items]
Health premium				$ 16,470	$ 35,131
Health premium earned per segment, Change %				(53.00%)

[1] Certain balances were retrospectively adjusted to give effect to the adoption of new accounting guidance as described in Note G- Adoption of New Accounting Standards