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Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2019 | Jan. 01, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Performance obligation, description of timing |  | one year or less |  |  |  |  |
Mortgage loans secured by residential real estate in process of foreclosure | [1] | $ 17,838 |  |  | $ 25,290 |  |
Lease right-of use assets |  | 203,910 |  |  |  |  |
Lease liabilities |  | 225,836 |  |  |  |  |
Loans, net of unearned income |  | 31,061,111 | [2] |  | 27,535,532 | [2] | $ 27,658,929
Undivided profits |  | $ 1,798,442 |  |  | 1,542,408 |  |
Deposit Bases |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Intangible assets, amortization period |  | 10 years |  |  |  |  |
Minimum | Furniture and Fixtures |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Useful life of premises and equipment |  | 3 years |  |  |  |  |
Minimum | Building |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Useful life of premises and equipment |  | 7 years |  |  |  |  |
Maximum | Furniture and Fixtures |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Useful life of premises and equipment |  | 15 years |  |  |  |  |
Maximum | Building |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Useful life of premises and equipment |  | 45 years |  |  |  |  |
Non-Accruing | Minimum |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Impaired commercial loans |  | $ 1,000 |  |  |  |  |
Accounting Standards Update 2016-02 |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Adjustment to reflect adoption of accounting standard |  |  |  |  | $ (1,011) |  |
Lease right-of use assets |  |  |  | $ 185,000 |  |  |
Lease liabilities |  |  |  | 204,000 |  |  |
Loans, net of unearned income |  |  |  | 3,450 |  |  |
Undivided profits |  |  |  | $ 1,011 |  |  |
Government Guaranteed Mortgage Loans upon Foreclosure Receivable |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Mortgage loans secured by residential real estate in process of foreclosure |  | 2,200 |  |  |  |  |
Non-Interest income |  |  |  |  |  |  |
Change in Accounting Estimate [Line Items] |  |  |  |  |  |  |
Accounts receivable, net |  | $ 8,700 |  |  |  |  |
[1] | December 31, 2019 and 2018 include $9.2 million and $9.7 million, respectively, of foreclosed residential real estate.
[2] | December 31, 2019 and 2018 include $18.8 million and $28.6 million, respectively, of held-to-maturity consumer mortgage loans secured by residential real estate in process of foreclosure.

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