Adjustments for Difference in Interim Medicare Part D Results for Segment Purposes and GAAP (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Disclosure [Line Items]
Benefit costs deferred	$ 25,047		$ 11,211
Government risk-sharing premium adjustment	(6,125)		(5,374)
Pre-tax addition to segment interim period income	18,922	[1]	5,837	[1],[2]
After tax amount	$ 12,299		$ 3,794

[1] Medicare Part D items adjusted to GAAP from the segment analysis, which matches expected benefits with policy premium.

[2] The 2011 balances have been retroactively adjusted to give effect to the adoption of new accounting guidance as described in Note F-Adoption of New Accounting Standard.