DEBT AND OTHER OBLIGATIONS - Amount of Collateral Pledged for Repurchase Agreements, Grouped by Asset Class (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	$ 153,681	$ 282,198
Securities lending transactions	80,194	62,840
Total securities	233,875	345,038
U.S. Treasury and agency securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	153,681	282,198
Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	60,358	55,720
Equity securities
Debt Instrument [Line Items]
Securities lending transactions	17,282	7,120
Other government related securities
Debt Instrument [Line Items]
Securities lending transactions	2,554
Overnight and Continuous
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	153,681	282,198
Securities lending transactions	80,194	62,840
Total securities	233,875	345,038
Overnight and Continuous \| U.S. Treasury and agency securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	153,681	282,198
Overnight and Continuous \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	60,358	55,720
Overnight and Continuous \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	17,282	7,120
Overnight and Continuous \| Other government related securities
Debt Instrument [Line Items]
Securities lending transactions	2,554
Up to 30 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Securities lending transactions	0	0
Total securities	0	0
Up to 30 days \| U.S. Treasury and agency securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Up to 30 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Up to 30 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Up to 30 days \| Other government related securities
Debt Instrument [Line Items]
Securities lending transactions	0
30-90 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Securities lending transactions	0	0
Total securities	0	0
30-90 days \| U.S. Treasury and agency securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
30-90 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
30-90 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
30-90 days \| Other government related securities
Debt Instrument [Line Items]
Securities lending transactions	0
Greater Than 90 days
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Securities lending transactions	0	0
Total securities	0	0
Greater Than 90 days \| U.S. Treasury and agency securities
Debt Instrument [Line Items]
Repurchase agreements and repurchase-to-maturity transactions	0	0
Greater Than 90 days \| Corporate securities
Debt Instrument [Line Items]
Securities lending transactions	0	0
Greater Than 90 days \| Equity securities
Debt Instrument [Line Items]
Securities lending transactions	0	$ 0
Greater Than 90 days \| Other government related securities
Debt Instrument [Line Items]
Securities lending transactions	$ 0

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- Definition

Amount, before effects of master netting arrangements, of funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial asset at a date certain for a specified price. Includes repurchase-to-maturity transactions and liabilities not subject to a master netting arrangement.

+ References

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral and funds outstanding borrowed in the form of a financial asset repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same financial assets at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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- Definition

Amount, before effects of master netting arrangements, of financial assets loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and financial assets transferred other than securities that qualify as secured borrowings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
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-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 7
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL34722452-111729

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