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.