Bonds and Notes Payable - Outstanding Debt Obligations (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 16,286,610	$ 17,824,087
Discount on bonds and notes payable and debt issuance costs	(171,341)	(192,998)
Bonds and notes payable, net	16,115,269	17,631,089
Unsecured line of credit
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 0	$ 0
Interest rate	0.00%	0.00%
Participation agreement
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 393,480	$ 253,969
Interest rate	2.41%	0.78%
Repurchase agreements
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 500,690	$ 483,848
Secured line of credit
Debt Instrument [Line Items]
Bonds and notes payable, gross		$ 5,000
Interest rate		1.91%
Federally insured \| Bonds and notes based on indices
Debt Instrument [Line Items]
Bonds and notes payable, gross	14,323,434	$ 15,887,295
Federally insured \| Bonds and notes based on auction
Debt Instrument [Line Items]
Bonds and notes payable, gross	221,385	248,550
Federally insured \| Variable-rate bonds and notes
Debt Instrument [Line Items]
Bonds and notes payable, gross	14,544,819	16,135,845
Federally insured \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Bonds and notes payable, gross	703,600	772,935
Federally insured \| Warehouse facilities
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 4,618	$ 5,048
Interest rate	1.64%	0.21%
Private education \| Variable-rate bonds and notes
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 24,737	$ 31,818
Private education \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Bonds and notes payable, gross	25,200	28,613
Private education \| Warehouse facilities
Debt Instrument [Line Items]
Bonds and notes payable, gross	$ 89,466	$ 107,011
Interest rate	1.71%	0.24%
Minimum \| Repurchase agreements
Debt Instrument [Line Items]
Interest rate	0.97%	0.66%
Minimum \| Federally insured \| Bonds and notes based on indices
Debt Instrument [Line Items]
Interest rate	1.22%	0.23%
Minimum \| Federally insured \| Bonds and notes based on auction
Debt Instrument [Line Items]
Interest rate	0.00%	0.00%
Minimum \| Federally insured \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Interest rate	1.42%	1.42%
Minimum \| Private education \| Variable-rate bonds and notes
Debt Instrument [Line Items]
Interest rate	3.10%	1.65%
Minimum \| Private education \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Interest rate	3.60%	3.60%
Maximum \| Repurchase agreements
Debt Instrument [Line Items]
Interest rate	2.81%	1.46%
Maximum \| Federally insured \| Bonds and notes based on indices
Debt Instrument [Line Items]
Interest rate	3.62%	2.10%
Maximum \| Federally insured \| Bonds and notes based on auction
Debt Instrument [Line Items]
Interest rate	2.30%	1.09%
Maximum \| Federally insured \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Interest rate	3.45%	3.45%
Maximum \| Private education \| Variable-rate bonds and notes
Debt Instrument [Line Items]
Interest rate	3.37%	1.85%
Maximum \| Private education \| Fixed rate bonds and notes
Debt Instrument [Line Items]
Interest rate	5.35%	5.35%

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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