RELATED-PARTY TRANSACTIONS - Beneficiaries of Common Shares Under Deferred Compensation Agreements (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Common stock owned by officer (in shares)	1,375	55,371
Fair value of PICO stock held in deferred compensation accounts	$ 17,600.00	$ 839,000
Former CEO
Related Party Transaction [Line Items]
Common stock owned by officer (in shares)		53,996
Mr. Webb, CEO
Related Party Transaction [Line Items]
Common stock owned by officer (in shares)	1,375	1,375