STATUTORY REPORTING, CAPITAL REQUIREMENTS AND DIVIDENDS AND RETAINED EARNINGS RESTRICTIONS (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory Accounting Practices [Line Items]
Payment of cash dividends	$ 32,662	$ 105,408	$ 27,337
United Fire & Casualty Company
Statutory Accounting Practices [Line Items]
Intercompany dividend payments that are eliminated in Consolidated Financial Statements	57,000	105,000	40,000
Subsidiaries
Statutory Accounting Practices [Line Items]
Intercompany dividend payments that are eliminated in Consolidated Financial Statements	6,300	$ 8,500	$ 13,300
State of Iowa Insurance Department
Statutory Accounting Practices [Line Items]
Statutory amount available for dividend payments	$ 154,200