Amount And Percentage Of Fixed Maturities by Rating (Detail) (USD $) In Thousands, unless otherwise specified			9 Months Ended
Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Extremely strong	Sep. 30, 2012 Very strong	Sep. 30, 2012 Strong	Sep. 30, 2012 Adequate	Sep. 30, 2012 Speculative	Sep. 30, 2012 Not rated
Rating			AAA	AA	A	BBB	BB & Below	NR
Fair Value	$ 2,085,058	$ 1,888,069	$ 348,008	$ 1,177,602	$ 380,992	$ 146,910	$ 14,508	$ 17,038
Percent of Total	100.00%		17.00%	56.00%	18.00%	7.00%	1.00%	1.00%

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details