Notes Payable - Borrowings (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Due within one year:
Current portion of medium-term notes	$ 7,063,602	$ 6,986,799
Weighted - average rate (as a percent)	1.19%	0.45%
Medium-term notes due in:
Two years	$ 4,356,442
Three years	2,755,310
Four years	2,646,648
Five years	2,750,521
Thereafter	4,265,636
Total due after one year	16,774,557
Total principal net of discounts	23,838,159	$ 22,758,533
Hedging adjustments	(364,064)	(42,377)
Total	$ 23,474,095	22,716,156
Weighted - average rate (as a percent)	1.45%
Total weighted - average rate (as a percent)	1.37%
Two years
Medium-term notes due in:
Weighted - average rate (as a percent)	1.13%
Three years
Medium-term notes due in:
Weighted - average rate (as a percent)	1.24%
Four years
Medium-term notes due in:
Weighted - average rate (as a percent)	1.06%
Five years
Medium-term notes due in:
Weighted - average rate (as a percent)	1.64%
Thereafter
Medium-term notes due in:
Weighted - average rate (as a percent)	2.03%
Discount notes
Due within one year:
Current portion of medium-term notes	$ 1,476,680	$ 2,167,979
Weighted - average rate (as a percent)	1.10%	0.05%
Short-term debt, average outstanding during the quarter	$ 1,733,373	$ 1,822,714
Weighted - average rate, average outstanding during the quarter (as a percent)	0.37%	0.08%
Medium-term notes
Due within one year:
Current portion of medium-term notes	$ 1,370,907	$ 837,580
Weighted - average rate (as a percent)	1.73%	0.09%
Short-term debt, average outstanding during the quarter	$ 942,055	$ 1,956,870
Weighted - average rate, average outstanding during the quarter (as a percent)	0.58%	0.12%
Medium-term notes due in:
Two years		$ 4,179,985
Three years		2,554,906
Four years		2,119,805
Five years		2,810,894
Thereafter		4,106,144
Total due after one year		$ 15,771,734
Weighted - average rate (as a percent)		1.10%
Total weighted - average rate (as a percent)		0.90%
Medium-term notes | Two years
Medium-term notes due in:
Weighted - average rate (as a percent)		0.81%
Medium-term notes | Three years
Medium-term notes due in:
Weighted - average rate (as a percent)		0.87%
Medium-term notes | Four years
Medium-term notes due in:
Weighted - average rate (as a percent)		0.85%
Medium-term notes | Five years
Medium-term notes due in:
Weighted - average rate (as a percent)		1.07%
Medium-term notes | Thereafter
Medium-term notes due in:
Weighted - average rate (as a percent)		1.69%
Current portion of medium-term notes
Due within one year:
Current portion of medium-term notes	$ 4,216,015	$ 3,981,240
Weighted - average rate (as a percent)	1.05%	0.75%