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DERIVATIVE INSTRUMENTS - Summary of Characteristics of Interest Rate Swaps (Details) - USD ($) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Interest Rate Swaps |  |
Derivative [Line Items] |  |
Current Notional | $ 34,329,650,000 | $ 74,146,350,000
Weighted Average Pay Rate | 0.92% | 1.84%
Weighted Average Receive Rate | 0.37% | 1.89%
Weighted Average Years to Maturity | 3 years 11 months 8 days | 4 years 2 months 23 days
Interest Rate Swaps | LIBOR |  |
Derivative [Line Items] |  |
Nonmonetary notional amount, percentage | 0.17 | 0.75
Interest Rate Swaps | Federal Funds Rate |  |
Derivative [Line Items] |  |
Nonmonetary notional amount, percentage | 0.72 |
Interest Rate Swaps | Overnight Index Swap |  |
Derivative [Line Items] |  |
Nonmonetary notional amount, percentage | 0.11 | 0.25
Interest Rate Swaps | 0 - 3 years |  |
Derivative [Line Items] |  |
Current Notional | $ 23,680,150,000 | $ 38,942,400,000
Weighted Average Pay Rate | 0.27% | 1.60%
Weighted Average Receive Rate | 0.11% | 1.84%
Weighted Average Years to Maturity | 1 year 11 months 15 days | 1 year 3 months 14 days
Minimum Maturity Period | 0 years | 0 years
Maximum Maturity Period | 3 years | 3 years
Interest Rate Swaps | 3 - 6 years |  |
Derivative [Line Items] |  |
Current Notional | $ 3,600,000,000 | $ 16,097,450,000
Weighted Average Pay Rate | 0.18% | 1.77%
Weighted Average Receive Rate | 0.09% | 1.87%
Weighted Average Years to Maturity | 4 years 2 months 15 days | 4 years 3 months 18 days
Minimum Maturity Period | 3 years | 3 years
Maximum Maturity Period | 6 years | 6 years
Interest Rate Swaps | 6 - 10 years |  |
Derivative [Line Items] |  |
Current Notional | $ 5,565,500,000 | $ 16,176,500,000
Weighted Average Pay Rate | 1.40% | 2.20%
Weighted Average Receive Rate | 0.62% | 2.02%
Weighted Average Years to Maturity | 7 years 9 months 3 days | 9 years
Minimum Maturity Period | 6 years | 6 years
Maximum Maturity Period | 10 years | 10 years
Interest Rate Swaps | Greater than 10 years |  |
Derivative [Line Items] |  |
Current Notional | $ 1,484,000,000 | $ 2,930,000,000
Weighted Average Pay Rate | 3.06% | 3.76%
Weighted Average Receive Rate | 0.36% | 1.86%
Weighted Average Years to Maturity | 20 years 6 months 7 days | 17 years 10 months 17 days
Minimum Maturity Period | 10 years | 10 years
Forward Starting Pay Fixed Swaps |  |
Derivative [Line Items] |  |
Current Notional | $ 0 | $ 0

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