Basis of Presentation and Accounting Policies (Schedule of Adoption) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses	$ 493,452		$ 281,402	$ 257,036	$ 250,555
Retained earnings	1,014,238		1,068,327
Total commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses	216,950		145,782	135,639	133,123
Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses	107,117		67,430	69,009	68,796
Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses	$ 169,385		$ 68,190	$ 52,388	$ 48,636
ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		$ 281,402
Reserve for unfunded commitments		1,375
Allowance for credit losses		282,777
Loans, net		36,881,048
Retained earnings		1,068,327
ASU 2016-13 | Total commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		145,782
ASU 2016-13 | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		67,430
ASU 2016-13 | Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		68,190
ASU 2016-13 | Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		82,994
Reserve for unfunded commitments		27,440
Allowance for credit losses		110,434
Loans, net		(20,767)
Retained earnings		(35,721)
ASU 2016-13 | Impact of ASC 326 Adoption | Total commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		(2,310)
ASU 2016-13 | Impact of ASC 326 Adoption | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		(651)
ASU 2016-13 | Impact of ASC 326 Adoption | Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		85,955
ASU 2016-13 | As Reported under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		364,396
Reserve for unfunded commitments		28,815
Allowance for credit losses		393,211
Loans, net		36,860,281
Retained earnings		1,032,606
ASU 2016-13 | As Reported under ASC 326 | Total commercial and industrial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		143,472
ASU 2016-13 | As Reported under ASC 326 | Total commercial real estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		66,779
ASU 2016-13 | As Reported under ASC 326 | Retail
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total allowance for loan losses		$ 154,145