SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Intangible Assets and EPS (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Business Acquisition
Goodwill	$ 46,062,000		$ 46,062,000
Indefinite-lived intangibles - state insurance licenses	7,500,000		7,500,000
Definite-lived intangibles, net of accumulated amortization of $3,572 at 3/31/20 and $3,470 at 12/31/19	463,000		565,000
Total intangibles	7,963,000		8,065,000
Goodwill and intangibles	54,025,000		54,127,000
Accumulated amortization of definite-lived intangibles	3,572,000		3,470,000
Amortization of intangible assets	100,000	$ 100,000
Basic EPS, Income (Numerator)
Income available to common shareholders	(61,267,000)	65,473,000
Diluted EPS, Income (Numerator)
Income available to common shareholders	$ (61,267,000)	$ 65,473,000
Basic EPS, Weighted Average Shares (Denominator)
Number of shares outstanding	44,920	44,536
Effect of Dilutive Securities, Shares (Denominator)
Stock options (in shares)		351
Diluted EPS, Weighted Average Shares (Denominator)
Number of shares outstanding	44,920	44,887
Basic EPS, Per Share Amount
Basic net earnings per share (in dollars per share)	$ (1.36)	$ 1.47
Diluted EPS, Per Share Amount
Diluted earnings per share (in dollars per share)	$ (1.36)	$ 1.46
Contractors Bonding and Insurance Company
Business Acquisition
Impairment of indefinite-lived intangible assets			0
Energy Surety
Business Acquisition
Goodwill	$ 25,706,000		25,706,000
Goodwill, Impairment Loss			0
Miscellaneous and Contract Surety
Business Acquisition
Goodwill	15,110,000		15,110,000
Goodwill, Impairment Loss			0
Small commercial
Business Acquisition
Goodwill	$ 5,246,000		5,246,000
Goodwill, Impairment Loss			$ 0