Schedule of Analysis Deferred Acquisition Costs (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Deferred Policy Acquisition Costs And Insurance Expenses [Line Items]
Deferred Acquisition Costs, Balance at beginning of year				$ 2,916,732				$ 2,869,546	$ 2,916,732		$ 2,869,546		$ 2,810,507
Deferred Acquisition Costs, Commissions									312,581		283,961		291,562
Deferred Acquisition Costs, Other expenses									168,237		157,864		149,351
Deferred Acquisition Costs, Total deferred costs									480,818		441,825		440,913
Deferred Acquisition Costs, Value of insurance purchased during year									175,257		0		0
Deferred Acquisition Costs, Foreign exchange adjustment									3,557		0		5,055
Deferred Acquisition Costs, Adjustment attributable to unrealized investment losses									7,234	[1]	0	[1]	0	[1]
Deferred Acquisition Costs, Total additions									666,866		441,825		445,968
Deferred Acquisition Costs, Amortized during period	(98,052)	(94,016)	(96,601)	(96,498)	(90,557)	(89,899)	(91,664)	(92,463)	(385,167)		(364,583)		(362,390)
Deferred Acquisition Costs, Foreign exchange adjustment									0		(1,765)		0
Deferred Acquisition Costs, Adjustment attributable to unrealized investment gains									0	[1]	(28,291)	[1]	(24,539)	[1]
Deferred Acquisition Costs, Total deductions									(385,167)		(394,639)		(386,929)
Deferred Acquisition Costs, Balance at end of period	$ 3,198,431				$ 2,916,732				$ 3,198,431		$ 2,916,732		$ 2,869,546

[1] Represents amounts pertaining to investments relating to universal life-type products.