BORROWINGS (Parent Company and Other IHC Entities) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total borrowings and other debt obligations	[1]	$ 48,135,215	$ 50,654,406
Short-term debt borrowings due February 2021
Debt Instrument [Line Items]
Stated interest rate		2.00%
Short-term borrowings, Balance		$ 124,067	$ 0
Effective Rate		2.00%	0.00%
Subsidiaries | 2.00% subordinated debt maturing through 2020
Debt Instrument [Line Items]
Stated interest rate		2.00%
Subordinated debt, Balance		$ 11	$ 602
Effective Rate		2.00%	2.00%
Subsidiaries | Short-term borrowing due within one year, maturing October 2020
Debt Instrument [Line Items]
Short-term borrowings, Balance		$ 8,000	$ 1,831
Effective Rate		0.50%	0.38%
Parent Company and Other Subsidiaries
Debt Instrument [Line Items]
Total borrowings and other debt obligations		$ 10,917,442	$ 9,951,647
Effective Rate		3.69%	3.68%
Senior Notes | 2.65% senior notes due April 2020
Debt Instrument [Line Items]
Stated interest rate		2.65%
Senior notes, Balance		$ 0	$ 999,502
Effective Rate		0.00%	2.82%
Senior Notes | 4.45% senior notes due December 2021
Debt Instrument [Line Items]
Stated interest rate		4.45%
Senior notes, Balance		$ 604,862	$ 604,172
Effective Rate		4.61%	4.61%
Senior Notes | 3.70% senior notes due March 2022
Debt Instrument [Line Items]
Stated interest rate		3.70%
Senior notes, Balance		$ 848,998	$ 849,465
Effective Rate		3.74%	3.74%
Senior Notes | 3.40% senior notes due January 2023
Debt Instrument [Line Items]
Stated interest rate		3.40%
Senior notes, Balance		$ 996,980	$ 996,043
Effective Rate		3.54%	3.54%
Senior Notes | 3.50% senior notes due June 2024
Debt Instrument [Line Items]
Stated interest rate		3.50%
Senior notes, Balance		$ 996,462	$ 995,797
Effective Rate		3.60%	3.60%
Senior Notes | 4.50% senior notes due July 2025
Debt Instrument [Line Items]
Stated interest rate		4.50%
Senior notes, Balance		$ 1,096,930	$ 1,096,508
Effective Rate		4.56%	4.56%
Senior Notes | 4.40% senior notes due July 2027
Debt Instrument [Line Items]
Stated interest rate		4.40%
Senior notes, Balance		$ 1,049,825	$ 1,049,813
Effective Rate		4.40%	4.40%
Senior Notes | 2.88% senior notes, due January 2024
Debt Instrument [Line Items]
Stated interest rate		2.88%
Senior notes, Balance		$ 750,000	$ 750,000
Effective Rate		2.88%	2.88%
Senior Notes | 5.83% senior notes, due March 2023
Debt Instrument [Line Items]
Stated interest rate		5.83%
Senior notes, Balance		$ 500,000	$ 0
Effective Rate		5.83%	0.00%
Senior Notes | 3.24% senior notes due November 2026
Debt Instrument [Line Items]
Stated interest rate		3.24%
Senior notes, Balance		$ 911,870	$ 907,844
Effective Rate		3.97%	3.97%
Senior Notes | 3.45% senior notes, due June 2025
Debt Instrument [Line Items]
Stated interest rate		3.45%
Senior notes, Balance		$ 994,599	$ 0
Effective Rate		3.58%	0.00%
Senior Notes | 3.50% senior notes, due April 2023
Debt Instrument [Line Items]
Stated interest rate		3.50%
Senior notes, Balance		$ 447,022	$ 0
Effective Rate		3.52%	0.00%
Senior Notes | Senior notes, due September 2020
Debt Instrument [Line Items]
Senior notes, Balance		$ 0	$ 112,358
Effective Rate		0.00%	3.36%
Senior Notes | Senior notes, due September 2020 | 3-month LIBOR
Debt Instrument [Line Items]
Basis spread on LIBOR (as a percent)		105.00%
Senior Notes | Senior notes, due June 2022
Debt Instrument [Line Items]
Senior notes, Balance		$ 427,916	$ 427,889
Effective Rate		2.05%	3.47%
Senior Notes | Senior notes, due June 2022 | 3-month LIBOR
Debt Instrument [Line Items]
Basis spread on LIBOR (as a percent)		100.00%
Senior Notes | Senior notes, due January 2023
Debt Instrument [Line Items]
Senior notes, Balance		$ 720,893	$ 720,861
Effective Rate		2.29%	3.29%
Senior Notes | Senior notes, due January 2023 | 3-month LIBOR
Debt Instrument [Line Items]
Basis spread on LIBOR (as a percent)		110.00%
Senior Notes | Senior notes, due July 2023
Debt Instrument [Line Items]
Senior notes, Balance		$ 439,007	$ 438,962
Effective Rate		2.29%	2.48%

[1] The Company has interests in certain Trusts that are considered VIEs for accounting purposes. At September 30, 2020 and December 31, 2019, LHFI included $22.7 billion and $26.5 billion, Operating leases assets, net included $16.2 billion and $16.5 billion, restricted cash included $1.8 billion and $1.6 billion, other assets included $870.2 million and $625.4 million, Borrowings and other debt obligations included $31.3 billion and $34.2 billion, and Other liabilities included $118.0 million and $188.1 million of assets or liabilities that were included within VIEs, respectively. See Note 7 to these Condensed Consolidated Financial Statements for additional information.