DEBT AND OTHER OBLIGATIONS - Repurchase Agreements, Securities Lending Transactions, and Repurchase-to-Maturity Transactions Accounted for as Secured Borrowings (Details) - Successor $ in Thousands	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Total borrowings	$ 861,732
U.S. Treasury and agency securities
Debt Instrument [Line Items]
Total borrowings	381,463
State and municipal securities
Debt Instrument [Line Items]
Total borrowings	0
Other asset-backed securities
Debt Instrument [Line Items]
Total borrowings	0
Corporate securities
Debt Instrument [Line Items]
Total borrowings	0
Equity securities
Debt Instrument [Line Items]
Total borrowings	0
Non-U.S. sovereign debt
Debt Instrument [Line Items]
Total borrowings	0
Mortgage loans
Debt Instrument [Line Items]
Total borrowings	480,269
Overnight and Continuous
Debt Instrument [Line Items]
Total borrowings	837,974
Overnight and Continuous | U.S. Treasury and agency securities
Debt Instrument [Line Items]
Total borrowings	357,705
Overnight and Continuous | State and municipal securities
Debt Instrument [Line Items]
Total borrowings	0
Overnight and Continuous | Other asset-backed securities
Debt Instrument [Line Items]
Total borrowings	0
Overnight and Continuous | Corporate securities
Debt Instrument [Line Items]
Total borrowings	0
Overnight and Continuous | Equity securities
Debt Instrument [Line Items]
Total borrowings	0
Overnight and Continuous | Non-U.S. sovereign debt
Debt Instrument [Line Items]
Total borrowings	0
Overnight and Continuous | Mortgage loans
Debt Instrument [Line Items]
Total borrowings	480,269
Up to 30 days
Debt Instrument [Line Items]
Total borrowings	23,758
Up to 30 days | U.S. Treasury and agency securities
Debt Instrument [Line Items]
Total borrowings	23,758
Up to 30 days | State and municipal securities
Debt Instrument [Line Items]
Total borrowings	0
Up to 30 days | Other asset-backed securities
Debt Instrument [Line Items]
Total borrowings	0
Up to 30 days | Corporate securities
Debt Instrument [Line Items]
Total borrowings	0
Up to 30 days | Equity securities
Debt Instrument [Line Items]
Total borrowings	0
Up to 30 days | Non-U.S. sovereign debt
Debt Instrument [Line Items]
Total borrowings	0
Up to 30 days | Mortgage loans
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | U.S. Treasury and agency securities
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | State and municipal securities
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | Other asset-backed securities
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | Corporate securities
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | Equity securities
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | Non-U.S. sovereign debt
Debt Instrument [Line Items]
Total borrowings	0
30 - 90 days | Mortgage loans
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | U.S. Treasury and agency securities
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | State and municipal securities
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | Other asset-backed securities
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | Corporate securities
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | Equity securities
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | Non-U.S. sovereign debt
Debt Instrument [Line Items]
Total borrowings	0
Greater Than 90 days | Mortgage loans
Debt Instrument [Line Items]
Total borrowings	$ 0