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Derivatives (Narrative) (Details) MMBTU in Thousands, Boe in Thousands, $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 USD ($) company | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) Boe MMBTU company | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($) Boe MMBTU company
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | $ 694,010 |  | $ 694,010 |  | $ 602,754
Derivative liabilities - Fair value | 561,788 |  | 561,788 |  | 424,828
Credit-risk-related contingent features |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Aggregate fair value of derivative instruments in net liability position | 82,400 |  | 82,400 |  | 107,400
Collateral posted | 81,100 |  | 81,100 |  | 106,800
Derivative instruments designated as hedging instruments |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 158 |  | 158 |  | 0
Notional Amount | 360,316 |  | 360,316 |  | 359,269
Derivative liabilities - Fair value | 1,149 |  | 1,149 |  | 2,099
Derivative instruments designated as hedging instruments | Fair Value Hedging | Interest Expense |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Gains or losses recognized on Consolidated Statement of Income related to the derivatives designated as fair value hedges |  | $ 112 |  | $ (1,600) |
Derivative instruments designated as hedging instruments | Fair Value Hedging | Interest Expense | Deposits |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Gains or losses recognized on Consolidated Statement of Income related to the derivatives designated as fair value hedges | 0 |  | 0 |  |
Derivative instruments designated as hedging instruments | Interest rate contracts | Cash Flow Hedging |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 0 |  | 0 |  | 0
Net unrealized losses, net of tax, recorded in AOCI expected to be reclassified into earnings during next 12 months | 625 |  | 625 |  |
Notional Amount | 275,000 |  | 275,000 |  | 275,000
Derivative liabilities - Fair value | 1,149 |  | 1,149 |  | 1,864
Derivative instruments designated as hedging instruments | Interest rate contracts | Fair Value Hedging |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 0 |  | 0 |  | 0
Derivative instruments designated as hedging instruments | Interest rate contracts | Fair Value Hedging | Interest Expense |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Change in unrealized gains or losses on fair value hedging instruments | 0 | $ 154 | 0 | $ 3,200 |
Derivatives not designated as hedging instruments |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 693,852 |  | 693,852 |  | 602,754
Notional Amount | 20,874,985 |  | 20,874,985 |  | 21,341,158
Derivative liabilities - Fair value | 560,639 |  | 560,639 |  | 422,729
Derivatives not designated as hedging instruments | Foreign exchange contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 31,717 |  | 31,717 |  | 30,300
Notional Amount | 3,047,846 |  | 3,047,846 |  | 3,108,488
Derivative liabilities - Fair value | 24,313 |  | 24,313 |  | 22,524
Derivatives not designated as hedging instruments | Interest rate contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 298,831 |  | 298,831 |  | 489,132
Notional Amount | 17,743,446 |  | 17,743,446 |  | 18,155,678
Derivative liabilities - Fair value | 212,179 |  | 212,179 |  | 315,834
Derivatives not designated as hedging instruments | Interest rate contracts | Financial Counterparty |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Notional Amount | 8,890,000 |  | 8,890,000 |  | 9,090,000
Derivatives not designated as hedging instruments | Interest rate contracts | LCH |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 16,000 |  | 16,000 |  | 1,300
Notional Amount | 2,860,000 |  | 2,860,000 |  | 2,980,000
Derivative liabilities - Fair value | 104,600 |  | 104,600 |  | 187,400
Derivatives not designated as hedging instruments | Credit contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 15 |  | 15 |  | 13
Notional Amount | 83,693 |  | 83,693 |  | 76,992
Derivative liabilities - Fair value | 120 |  | 120 |  | 206
Derivatives not designated as hedging instruments | Credit contracts | RPAs - protection sold |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Maximum exposure of RPAs with protection sold | $ 4,500 |  | $ 4,500 |  | $ 6,000
Weighted average remaining maturity of outstanding RPAs |  |  | 3 years 4 months 24 days |  | 3 years 6 months
Derivatives not designated as hedging instruments | Equity, Public Companies |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Number of companies that issued the equity (issuers portion only) | company | 1 |  | 1 |  | 2
Derivatives not designated as hedging instruments | Equity, Private Companies |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Number of companies that issued the equity (issuers portion only) | company | 12 |  | 12 |  | 17
Derivatives not designated as hedging instruments | Equity contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | $ 226 |  | $ 226 |  | $ 858
Notional Amount | 0 |  | 0 |  | 0
Derivative liabilities - Fair value | 0 |  | 0 |  | 0
Derivatives not designated as hedging instruments | Commodity contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 363,063 |  | 363,063 |  | 82,451
Notional Amount | 0 |  | 0 |  | 0
Derivative liabilities - Fair value | 324,027 |  | 324,027 |  | 84,165
Derivatives not designated as hedging instruments | Commodity contracts | Chicago Mercantile Exchange (CME) |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative assets - Fair value | 8,800 |  | 8,800 |  | 7,900
Derivative liabilities - Fair value | 41,200 |  | 41,200 |  | 3,700
Derivative assets (liabilities), at fair value, net | $ 7,500 |  | $ 7,500 |  | $ 0
Derivatives not designated as hedging instruments | Commodity contracts | Chicago Mercantile Exchange (CME) | Oil |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, nonmonetary notional amount, energy measure | Boe |  |  | 1,070 |  | 1,275
Derivatives not designated as hedging instruments | Commodity contracts | Chicago Mercantile Exchange (CME) | Natural gas |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Derivative, nonmonetary notional amount, energy measure | MMBTU |  |  | 15,740 |  | 29,733
Maximum | Derivatives not designated as hedging instruments | Foreign exchange contracts |  |  |  |  |
Derivative [Line Items] |  |  |  |  |
Original maturity (in years) |  |  | 1 year |  | 1 year

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