Significant Accounting Policies (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012 Integer	Dec. 31, 2011	Dec. 31, 2010
Number of Operating Segments	3
Policy Loans	$ 3,133.8	$ 3,051.4
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	705.0	670.9
Present Value of Future Insurance Profits	23.5	30.3
Accumulated Amortization of Other Deferred Costs	131.5	119.3
Present Value of Future Insurance Profits, Amortization Expense	7.5	7.4	7.4
Deferred Revenue and Credits	67.4	81.0
Premium tax expense	136.0	134.9	129.4
Assets, Participation Fund Account (PFA)	380.4	385.5
Ceded Policy Loans [Member]
Policy Loans	$ 2,912.7	$ 2,838.3

Seperate fund for mutual policies in-force.

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- Definition

Taxes incurred for premium written during the period.

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No definition available.

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- Definition

Accumulated amortization of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs, deferred acquisition costs of insurance companies, or deferred leasing costs for real estate operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Regulation S-X (SX)

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- Definition

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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-Publisher SEC

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- Definition

Total carrying amount of consideration received or receivable as of the balance sheet date representing potential earnings that were not as yet recognized as revenue or other forms of income in conformity with GAAP.

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- Definition

Gross amount of loans made to policy and contract holders using their life insurance contracts' cash value or separate accounts as collateral.

+ References

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-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

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-Chapter 11

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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- Definition

Carrying amount as of the balance sheet date of the present value of the future profits asset (also known as value of business acquired).

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The amount of the present value of future profits asset that was amortized during the period, generally in proportion to related revenue earned, estimated gross profits, or over the customer relationship or some other period.

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