OFFSETTING OF ASSETS AND LIABILITIES - Schedule of Derivative Instruments by Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Offsetting of Assets
Gross Amounts of Recognized Assets, Subject to a master netting arrangement or similar arrangement	$ 429,369	$ 417,769
Gross Amounts of Recognized Assets, Not subject to a master netting arrangement or similar arrangement	120,172	124,474
Gross Amounts of Recognized Assets	549,541	542,243
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	429,369	417,769
Net Amounts of Assets Presented in the Statement of Financial Position	549,541	542,243
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	202,402	171,384
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	113,092	100,890
Derivative Asset, Fair Value, Amount Offset Against Collateral	113,875	145,495
Net Amount	234,047	269,969
Free-Standing derivatives
Offsetting of Assets
Gross Amounts of Recognized Assets, Subject to a master netting arrangement or similar arrangement	429,369	417,769
Gross Amounts Offset in the Statement of Financial Position	0	0
Net Amounts of Assets Presented in the Statement of Financial Position	429,369	417,769
Gross Amounts Not Offset in the Statement of Financial Position, Financial Instruments	202,402	171,384
Gross Amounts Not Offset in the Statement of Financial Position, Cash Collateral Received	113,092	100,890
Derivative Asset, Fair Value, Amount Offset Against Collateral	113,875	145,495
Embedded derivative - Modco reinsurance treaties
Offsetting of Assets
Gross Amounts of Recognized Assets, Not subject to a master netting arrangement or similar arrangement	676	2,573
Embedded derivative - GLWB
Offsetting of Assets
Gross Amounts of Recognized Assets, Not subject to a master netting arrangement or similar arrangement	119,347	121,752
Other
Offsetting of Assets
Gross Amounts of Recognized Assets, Not subject to a master netting arrangement or similar arrangement	$ 149	$ 149