Summary of Significant Accounting Policies New Accounting Pronouncements or Change in Accounting Principle (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2020 USD ($) Segment	Mar. 31, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of portfolio segments | Segment	2
Allowance for credit losses on loans and leases, forecast perod	2 years
Allowance for credit losses on loans and leases, historical loss rate period	1 year
Allowance for credit losses on investment securities held-to-maturity, long-run loss rate period	3 years
Allowance for credit losses on investment securities held-to-maturity	$ (309)	$ (312)		$ 0
Allowance for credit losses on loans and leases				(209,096)
Deferred Tax Assets, Tax Deferred Expense				61,975
Accrued expenses and other liabilities	224,955			153,161
Retained earnings	2,024,487			$ 2,061,352
Accounting Standards Update 2016-13 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on investment securities held-to-maturity	(397)		$ (397)
Allowance for credit losses on loans and leases	(57,568)		(266,664)
Deferred Tax Assets, Tax Deferred Expense	15,891		77,866
Accrued expenses and other liabilities	9,139		162,300
Retained earnings	$ (51,213)		$ 2,010,139