Summary of Amounts Ceded to Allstate Life Insurance Company (Detail) (Allstate Life Insurance Company, USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allstate Life Insurance Company
Related Party Transaction [Line Items]
Premiums and contract charges	$ 908,459	$ 833,149	$ 782,113
Interest credited to contractholder funds, contract benefits and expenses	$ 1,369,305	$ 1,408,953	$ 1,683,487

Interest credited to contractholder funds, contract benefits and expenses that are assumed and expensed by another insurer as a result of reinsurance arrangements.

No definition available.

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Namespace Prefix:	ck0000910739_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration