Fair Value of Financial Instruments - Summary of Estimated Fair Values of Financial Instruments not Carried at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity securities	$ 41,186,735	$ 17,216,871
Net loans	47,283,415	44,733,723
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	21,254,859	17,674,763
Held-to-maturity securities	41,164,620	16,592,153
Non-marketable securities not measured at net asset value	379,224	240,761
Non-marketable securities measured at net asset value	426,306	390,658
FHLB and Federal Reserve Bank stock	83,355	61,232
Non-maturity deposits	123,454,403	101,293,346
Time deposits	695,703	688,461
Commitments to extend credit	0	0
Carrying Amount \| Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	38,434	20,553
Carrying Amount \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	348,441	348,348
Carrying Amount \| 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	495,387	495,280
Carrying Amount \| 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	494,355
Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	21,254,859	17,674,763
Held-to-maturity securities	41,186,735	17,216,871
Non-marketable securities not measured at net asset value	379,224	240,761
Non-marketable securities measured at net asset value	426,306	390,658
FHLB and Federal Reserve Bank stock	83,355	61,232
Non-maturity deposits	123,454,403	101,293,346
Time deposits	394,574	501,853
Commitments to extend credit	39,003	36,672
Estimate of Fair Value Measurement \| Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	38,434	20,553
Estimate of Fair Value Measurement \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	378,242	382,855
Estimate of Fair Value Measurement \| 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	521,205	563,840
Estimate of Fair Value Measurement \| 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	463,625
Estimate of Fair Value Measurement \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	21,254,859	17,674,763
Held-to-maturity securities	0	0
Non-marketable securities not measured at net asset value	0	0
Non-marketable securities measured at net asset value	0	0
FHLB and Federal Reserve Bank stock	0	0
Non-maturity deposits	123,454,403	101,293,346
Time deposits	0	0
Commitments to extend credit	0	0
Estimate of Fair Value Measurement \| Level 1 \| Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	0	0
Estimate of Fair Value Measurement \| Level 1 \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	0
Estimate of Fair Value Measurement \| Level 1 \| 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	0
Estimate of Fair Value Measurement \| Level 1 \| 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0
Estimate of Fair Value Measurement \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Held-to-maturity securities	41,186,735	17,216,871
Non-marketable securities not measured at net asset value	0	0
Non-marketable securities measured at net asset value	0	0
FHLB and Federal Reserve Bank stock	0	0
Non-maturity deposits	0	0
Time deposits	394,574	501,853
Commitments to extend credit	0	0
Estimate of Fair Value Measurement \| Level 2 \| Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	38,434	20,553
Estimate of Fair Value Measurement \| Level 2 \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	378,242	382,855
Estimate of Fair Value Measurement \| Level 2 \| 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	521,205	563,840
Estimate of Fair Value Measurement \| Level 2 \| 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	463,625
Estimate of Fair Value Measurement \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	0	0
Held-to-maturity securities	0	0
Non-marketable securities not measured at net asset value	379,224	240,761
Non-marketable securities measured at net asset value	0	0
FHLB and Federal Reserve Bank stock	83,355	61,232
Non-maturity deposits	0	0
Time deposits	0	0
Commitments to extend credit	39,003	36,672
Estimate of Fair Value Measurement \| Level 3 \| Short-term borrowings
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term borrowings	0	0
Estimate of Fair Value Measurement \| Level 3 \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	0
Estimate of Fair Value Measurement \| Level 3 \| 3.125% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0	0
Estimate of Fair Value Measurement \| Level 3 \| 1.800% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes	0
Commercial loans \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	42,264,653	39,886,296
Commercial loans \| Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	43,438,142	40,412,490
Commercial loans \| Estimate of Fair Value Measurement \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	0	0
Commercial loans \| Estimate of Fair Value Measurement \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	0	0
Commercial loans \| Estimate of Fair Value Measurement \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	43,438,142	40,412,490
Consumer loans \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	5,018,762	4,847,427
Consumer loans \| Estimate of Fair Value Measurement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	5,158,216	4,911,451
Consumer loans \| Estimate of Fair Value Measurement \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	0	0
Consumer loans \| Estimate of Fair Value Measurement \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	0	0
Consumer loans \| Estimate of Fair Value Measurement \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net loans	$ 5,158,216	$ 4,911,451

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Deposits, No Stated Maturity

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Fair Value, Investments, Entities that Calculate Net Asset Value, Non-Marketable Securities

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The amount shown on the books that a bank with insufficient reserves borrows, at the federal funds rate, from another bank to meet its reserve requirements and the amount of securities that an institution sells and agrees to repurchase at a specified date for a specified price, net of any reductions or offsets. Also reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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- Definition

Investment in Federal Home Loan Bank Stock and Federal Reserve Bank, Fair Value Disclosure

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Non-marketable securities accounted for under cost and equity method accounting

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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