Discontinued Operations and Assets and Liabilities Held-for-Sale - Income Statement and Balance Sheet disclosures (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net income (loss) from discontinued operations, net of tax	$ (5,269)		$ 2,710	$ 3,053	$ 4,195
Gain (loss) on sale and impairment loss on classification of assets as held-for-sale, net of tax	2,094		2	(9,309)	(1,858)
Net income (loss) from discontinued operations, net of tax	(3,175)		2,712	(6,256)	2,337
Real estate assets held-for-sale:
Cash and cash equivalents	0		28,024	0	28,024
Assets held-for-sale						$ 440,689
Real estate liabilities held-for-sale:
Liabilities held-for-sale						207,566
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue	39,482		95,544	247,719	246,656
Other	20		204	506	253
Cost of sales and expenses	45,881		92,692	244,293	242,019
General, administrative, and other	11,245		4,612	29,618	19,331
Sales and marketing	2,415		4,939	13,784	14,035
Impairment loss on long-lived assets		$ 11,400	4,416	102	6,812
Income (loss) before income taxes	(6,399)		2,852	3,426	4,637
Benefit (provision) for federal and state income taxes	1,130		(124)	(360)	(340)
Net income (loss) from discontinued operations, net of tax	(5,269)		2,710	3,053	4,195	13,899	$ (24,310)	$ (23,700)
Gain (loss) on sale and impairment loss on classification of assets as held-for-sale, net of tax	2,094			(9,311)		(1,775)	(18,729)
Income (loss) on sale of discontinued agribusiness operations, net of tax			2	2	(1,858)
Net income (loss) from discontinued operations, net of tax	(3,175)		2,712	(6,256)	2,337	12,124	$ (43,039)	$ (23,700)
Net (income) loss from discontinued operations attributable to noncontrolling interests	1,645		(1,043)	(1,150)	(1,676)
Net income (loss) from discontinued operations attributable to PICO Holdings, Inc.	(1,530)		1,669	(7,406)	661
Real estate assets held-for-sale:
Assets held-for-sale						440,689
Real estate liabilities held-for-sale:
Liabilities held-for-sale						207,566
Real Estate Operations | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenue	39,462		95,340	247,213	246,403
Cost of sales and expenses	32,221		78,725	200,789	201,841
Net income (loss) from discontinued operations, net of tax	(5,269)		2,728	3,066	4,297
Real estate assets held-for-sale:
Cash and cash equivalents						40,931
Real estate						373,207
Accounts receivable						5,628
Other assets						14,418
Valuation allowance on assets held-for-sale
Assets held-for-sale						434,184
Real estate liabilities held-for-sale:
Debt, net						160,994
Account payable and accrued expenses						34,025
Other liabilities						12,271
Liabilities held-for-sale						207,290
Agribusiness Operations | Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net income (loss) from discontinued operations, net of tax			$ (18)	$ (13)	$ (102)
Real estate assets held-for-sale:
Assets held-for-sale						6,505
Real estate liabilities held-for-sale:
Liabilities held-for-sale						$ 276