INVESTMENTS - Other Invested Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other invested assets
Other Investments	$ 51,542	$ 33,808
Qualified Affordable Housing Project Investments, Commitment	7,400
Investments pledged as collateral	$ 16,100
Investment in Federal Home Loan Bank Stock	us-gaap:AssetPledgedAsCollateralMember
Federal Home Loan Bank Borrowings, Fair Value Disclosure	$ 0
Investment In Low Income Housing Tax Credit Partnership Net Of Amortization Member
Other invested assets
Other Investments	20,300	15,500
Qualified Affordable Housing Project Investments, Commitment	7,400
Total tax benefit on investments in housing tax credit partnership	2,200	$ 2,400	$ 1,900
Investment in Private Funds
Other invested assets
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 18,800