Schedule IV - Reinsurance (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	$ 2,812,248	[1]	$ 2,607,058	[1]	$ 2,608,997	[1]
Ceded to Other Companies	9,821	[1],[2]	7,001	[1],[2]	7,287	[1],[2]
Assumed from Other Companies	30,725	[1]	31,311	[1]	23,419	[1]
Net Amount	2,833,152	[1]	2,631,368	[1]	2,625,129	[1]
Percentage of Amount Assumed to Net	1.10%	[1]	1.20%	[1]	0.90%	[1]
Life Insurance in Force
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	150,107,614	[1]	144,778,793	[1]	140,653,839	[1]
Ceded to Other Companies	800,905	[1],[2]	738,935	[1],[2]	722,577	[1],[2]
Assumed from Other Companies	4,138,180	[1]	4,414,247	[1]	4,743,222	[1]
Net Amount	153,444,889	[1]	148,454,105	[1]	144,674,484	[1]
Percentage of Amount Assumed to Net	2.70%	[1]	3.00%	[1]	3.30%	[1]
Life Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	1,762,640	[1]	1,675,307	[1]	1,618,973	[1]
Ceded to Other Companies	7,592	[1],[2]	4,716	[1],[2]	4,684	[1],[2]
Assumed from Other Companies	30,725	[1]	31,311	[1]	23,419	[1]
Net Amount	1,785,773	[1]	1,701,902	[1]	1,637,708	[1]
Percentage of Amount Assumed to Net	1.70%	[1]	1.80%	[1]	1.40%	[1]
Health Insurance
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Gross Amount	1,049,608	[1]	931,751	[1]	990,024	[1]
Ceded to Other Companies	2,229	[1],[2]	2,285	[1],[2]	2,603	[1],[2]
Assumed from Other Companies	0	[1]	0	[1]	0	[1]
Net Amount	$ 1,047,379	[1]	$ 929,466	[1]	$ 987,421	[1]
Percentage of Amount Assumed to Net	0.00%	[1]	0.00%	[1]	0.00%	[1]

[1] Excludes policy charges of $23,310, $24,950, and $26,629 in each of the years 2012, 2011, and 2010, respectively.

[2] No amounts have been netted against ceded premium