Commitments, Off-Balance Sheet Arrangements, Legal Proceedings and Regulatory Matters, Summary of Lending Related and Other Commitments (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Schedule of lending-related and other commitments [Line Items]
Expense Related to Qualified Affordable Housing Projects		$ 5,000	$ 5,000	$ 10,000	$ 9,000
Lending related commitments, fair value		0		0		$ 0
Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale
Summary of lending-related and other commitments
Lending related commitments	[1],[2]	8,902,027		8,902,027		8,720,293
Commercial Letters Of Credit
Summary of lending-related and other commitments
Lending related commitments	[1]	6,951		6,951		7,599
Standby Letters of Credit
Summary of lending-related and other commitments
Lending related commitments	[3]	264,541		264,541		255,904
Standby letters of credit, fair value		$ 3,000		$ 3,000		$ 2,000

[1] (a) These off-balance sheet financial instruments are exercisable at the market rate prevailing at the date the underlying transaction will be completed and, thus, are deemed to have no current fair value, or the fair value is based on fees currently charged to enter into similar agreements and is not material at June 30, 2019 or December 31, 2018.

[2] (b) Interest rate lock commitments to originate residential mortgage loans held for sale are considered derivative instruments and are disclosed in Note 10.

[3] (c) The Corporation has established a liability of $3 million and $2 million at June 30, 2019 and December 31, 2018, respectively, as an estimate of the fair value of these financial instruments.