Amount And Percentage Of Fixed Maturities And Short-term Investments (Detail) (USD $) In Thousands, unless otherwise specified			6 Months Ended
Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Extremely strong	Jun. 30, 2012 Very strong	Jun. 30, 2012 Strong	Jun. 30, 2012 Adequate	Jun. 30, 2012 Speculative	Jun. 30, 2012 Not rated
Rating			AAA	AA	A	BBB	BB & Below	NR
Fair Value	$ 2,024,429	$ 1,888,069	$ 341,094	$ 1,150,879	$ 381,490	$ 132,820	$ 14,282	$ 3,864
Percent of Total	100.00%		17.00%	56.00%	19.00%	7.00%	1.00%	0.00%

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

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