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SCHEDULE II - Condensed Financial Information Of Registrant Condensed Financial Information Of Registrant - Additional Information (Detail) - USD ($) $ in Billions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 01, 2015
Significant Accounting Policies [Line Items]
Securities Held In Consolidated Non-Insurance Subsidiary	$ 1.6	$ 1.3
ARX Holding Corp.
Significant Accounting Policies [Line Items]
Equity interest percentage	69.00%	69.20%	69.20%	5.00%
Parent Company
Significant Accounting Policies [Line Items]
Securities Held In Consolidated Non-Insurance Subsidiary	$ 1.6	$ 1.3

X

- Definition

Securities held in the portfolio of a consolidated, non-insurance subsidiary of the holding company, net of any unsettled security transactions.

+ References

No definition available.

+ Details

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Balance Type:	debit
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X

- Definition

Significant Accounting Policies [Line Items]

+ References

No definition available.

+ Details

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X

- Definition

Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date.

+ References

No definition available.

+ Details

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X

- Details

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X

- Details

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