SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Catastrophe Exposures (Details) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
California earthquake
Catastrophe Exposures
Catastrophe reinsurance	$ 300
First-dollar retention	25
Non-California earthquake
Catastrophe Exposures
Catastrophe reinsurance	325
First-dollar retention	25
Other perils
Catastrophe Exposures
Catastrophe reinsurance	225
First-dollar retention	$ 25

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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