OFFSETTING OF ASSETS AND LIABILITIES - Offsetting of Derivative Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Offsetting of Derivative Assets
Other long-term investments	$ 414,827	$ 629,537
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	414,827	629,537
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	70,322	242,105
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	99,199	108,830
Net Amount	245,306	278,602
Free-Standing derivatives
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets, subject to master netting arrangement	263,349	468,871
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	263,349	468,871
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, not subject to master neting arrangement	70,322	242,105
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	99,199	108,830
Net Amount	93,828	117,936
Total derivatives, subject to a master netting arrangement or similar arrangement
Offsetting of Derivative Assets
Gross Amounts of Recognized Assets, subject to master netting arrangement	263,349	468,871
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	263,349	468,871
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments, not subject to master neting arrangement	70,322	242,105
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	99,199	108,830
Net Amount	93,828	117,936
Embedded derivative - Modco reinsurance treaties
Offsetting of Derivative Assets
Other long-term investments	7,072	1,009
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	7,072	1,009
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	0	0
Net Amount	7,072	1,009
Embedded derivative - GLWB
Offsetting of Derivative Assets
Other long-term investments	54,221	67,879
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	54,221	67,879
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	0	0
Net Amount	54,221	67,879
Derivatives with PLC
Offsetting of Derivative Assets
Other long-term investments	90,049	91,578
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	90,049	91,578
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	0	0
Net Amount	90,049	91,578
Other
Offsetting of Derivative Assets
Other long-term investments	136	200
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	136	200
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	0	0
Net Amount	136	200
Total derivatives, not subject to a master netting arrangement or similar arrangement
Offsetting of Derivative Assets
Other long-term investments	151,478	160,666
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position, Including not subject to master netting arrangement	151,478	160,666
Gross Amounts Not Offset in the statement of Financial Position, Financial Instruments, subject to master netting arrangement	0	0
Gross Amounts Not Offset in the Statement of Financial Position, Collateral Received	0	0
Net Amount	$ 151,478	$ 160,666

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