SCHEDULE VI-SUPPLEMENTARY INFORMATION CONCERNING PROPERTY-CASUALTY INSURANCE OPERATIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Claims and claim adjustment expenses incurred related to:
Current accident year	$ 391,772	$ 364,472	$ 361,451
Prior accident years	(41,994)	(65,427)	(64,842)
Amortization of deferred acquisition costs	249,612	241,078	229,283
Consolidated property-casualty insurance operations
SUPPLEMENTARY INFORMATION CONCERNING PROPERTY-CASUALTY INSURANCE OPERATIONS
Deferred policy acquisition costs	73,147	69,829	65,123
Claims and claim adjustment expense reserves	1,139,337	1,103,785	1,121,040
Unearned premiums, gross	433,777	422,094	401,412
Net premiums earned	728,608	700,161	687,375
Net investment income	53,075	54,644	55,608
Claims and claim adjustment expenses incurred related to:
Current accident year	391,772	364,472	361,451
Prior accident years	(41,994)	(65,427)	(64,842)
Amortization of deferred acquisition costs	249,612	241,078	229,283
Paid claims and claims adjustment expenses	304,606	279,038	285,184
Net premiums written	$ 740,952	$ 721,971	$ 703,152