Summary Of Fixed Maturities And Equity Securities Available For Sale By Component (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 11,089,961
Gross Unrealized Gains	1,393,449
Gross Unrealized Losses	(157,906)
Fair Value	12,325,504
U.S. Government Direct, Guaranteed, And Government-Sponsored Enterprises
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	29,677
Gross Unrealized Gains	1,473
Gross Unrealized Losses	(9)
Fair Value	31,141
% of Total Fixed Maturities	1.00%	[1]
States, Municipalities, And Political Subdivisions
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,213,004
Gross Unrealized Gains	160,016
Gross Unrealized Losses	(415)
Fair Value	1,372,605
% of Total Fixed Maturities	11.00%	[1]
Foreign Governments
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	21,738
Gross Unrealized Gains	1,135
Gross Unrealized Losses	0
Fair Value	22,873
% of Total Fixed Maturities	0.00%	[1]
Corporates
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	8,593,737
Gross Unrealized Gains	1,193,283
Gross Unrealized Losses	(89,954)
Fair Value	9,697,066
% of Total Fixed Maturities	79.00%	[1]
Collateralized Debt Obligations
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	62,495
Gross Unrealized Gains	0
Gross Unrealized Losses	(32,538)
Fair Value	29,957
% of Total Fixed Maturities	0.00%	[1]
Other Asset-Backed Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	37,000
Gross Unrealized Gains	2,665
Gross Unrealized Losses	(1,275)
Fair Value	38,390
% of Total Fixed Maturities	0.00%	[1]
Redeemable Preferred Stocks
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	1,117,435
Gross Unrealized Gains	32,878
Gross Unrealized Losses	(33,661)
Fair Value	1,116,652
% of Total Fixed Maturities	9.00%	[1]
Total Fixed Maturities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	11,075,086
Gross Unrealized Gains	1,391,450
Gross Unrealized Losses	(157,852)
Fair Value	12,308,684
% of Total Fixed Maturities	100.00%	[1]
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	14,875
Gross Unrealized Gains	1,999
Gross Unrealized Losses	(54)
Fair Value	$ 16,820

[1] At fair value