Business Segments - Reconciliation of Health Premium Included in the segment Analysis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Health premium	$ 316,765	$ 329,863	[1]
Health premium earned per segment, Change %	(4.00%)
Medicare Part D [Member]
Segment Reporting Information [Line Items]
Health premium	79,347	83,033
Health premium earned per segment, Change %	(4.00%)
Other Health [Member]
Segment Reporting Information [Line Items]
Health premium	228,673	219,435
Health premium earned per segment, Change %	4.00%
Part D risk sharing adjustment [Member]
Segment Reporting Information [Line Items]
Health premium	$ 8,745	$ 27,395
Health premium earned per segment, Change %	(68.00%)

[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