Basis Of Presentation (Details) - USD ($)	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Basis of Accounting [Line Items]
Total shareholders' equity	$ 9,591,292,000			$ 9,132,925,000	$ 8,983,258,000
Operating lease right of use assets	149,206,000			161,435,000				$ 69,869,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]								Other assets
Operating lease liabilities	163,329,000			169,909,000				$ 77,270,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]								Other liabilities
Retained Earnings [Member]
Basis of Accounting [Line Items]
Total shareholders' equity	$ 10,565,792,000	$ 10,384,645,000	$ 10,255,692,000	10,306,571,000	$ 10,152,118,000	$ 10,104,716,000	$ 9,828,847,000	$ 9,531,433,000
Retained Earnings [Member] | Cumulative Effect Period Of Adoption Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Basis of Accounting [Line Items]
Total shareholders' equity				$ (4,214,000)				$ 0