SCHEDULE VI-SUPPLEMENTARY INFORMATION CONCERNING PROPERTY-CASUALTY INSURANCE OPERATIONS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Claims and claim adjustment expenses incurred related to:
Current accident year	$ 478,143	$ 440,452	$ 391,772
Prior accident years	(49,950)	(38,868)	(41,994)
Amortization of deferred acquisition costs	267,738	252,515	249,612
Consolidated property-casualty insurance operations
SUPPLEMENTARY INFORMATION CONCERNING PROPERTY-CASUALTY INSURANCE OPERATIONS
Deferred policy acquisition costs	84,934	77,716	73,147
Claims and claim adjustment expense reserves	1,461,348	1,271,503	1,139,337
Unearned premiums, gross	496,505	451,449	433,777
Net premiums earned	791,366	737,937	728,608
Net investment income	62,085	54,876	53,075
Claims and claim adjustment expenses incurred related to:
Current accident year	478,143	440,452	391,772
Prior accident years	(49,950)	(38,868)	(41,994)
Amortization of deferred acquisition costs	267,738	252,515	249,612
Paid claims and claims adjustment expenses	301,356	283,185	304,606
Net premiums written	$ 823,175	$ 749,854	$ 740,952