New Accounting Pronouncement - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended
	Jan. 02, 2020	Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Debt securities held to maturity allowance for credit loss			$ 12,735	$ 0
Recorded investment current			26,710,019	25,603,271
Stockholders equity		$ 5,669,605	$ 5,780,165	6,016,779	$ 5,719,834	$ 5,440,060	$ 5,435,057
Cumulative effect adoption adjustment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Stockholders equity		(205,800)		$ (205,842)			$ 4,905
Unfunded loan commitment
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit loss, increase (decrease)	$ (9,000)
Loan portfolio
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit loss, increase (decrease)	315,000
ASU 2016-13
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accruing loans past-due 90 days or more	144,000
Non-accrual loans	278,000
Recorded investment current	134,000
ASC Subtopic 310-30
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Allowance for credit loss, increase (decrease)		$ 17,000
Accruing loans past-due 90 days or more	144,000
Recorded investment current	$ 134,000