Fair Value of Assets & Liabilities - Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	$ 1,116,450	$ 1,346,207
Loans held-for-sale	13,263	14,033
Securities available-for-sale	5,476,156	4,445,403
Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	13,263	14,033
Securities available-for-sale	5,476,156	4,445,403
Total other assets	670,968	252,573
Total assets	7,276,837	6,058,216
Total other liabilities	94,389	67,480
Total liabilities	327,131	573,061
Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	0	0
Securities available-for-sale	0	0
Total other assets	106,672	90,098
Total assets	106,672	90,098
Total other liabilities	30,483	19,807
Total liabilities	30,483	19,807
Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	0	0
Securities available-for-sale	5,450,710	4,426,267
Total other assets	564,126	162,475
Total assets	7,130,658	5,934,008
Total other liabilities	45,091	24,878
Total liabilities	277,833	530,459
Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Loans held-for-sale	13,263	14,033
Securities available-for-sale	25,446	19,136
Total other assets	170	0
Total assets	39,507	34,110
Total other liabilities	18,815	22,795
Total liabilities	18,815	22,795
Deferred compensation mutual funds | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	48,572	46,815
Deferred compensation mutual funds | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	48,572	46,815
Deferred compensation mutual funds | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Deferred compensation mutual funds | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Derivatives, forwards and futures | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	35,408	20,640
Total other liabilities	30,483	19,807
Derivatives, forwards and futures | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	35,408	20,640
Total other liabilities	30,483	19,807
Derivatives, forwards and futures | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Total other liabilities	0	0
Derivatives, forwards and futures | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Total other liabilities	0	0
Derivatives, interest rate contracts | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	563,866	162,413
Total other liabilities	44,722	24,412
Derivatives, interest rate contracts | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Total other liabilities	0	0
Derivatives, interest rate contracts | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	563,866	162,413
Total other liabilities	44,722	24,412
Derivatives, interest rate contracts | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Total other liabilities	0	0
Derivatives, other | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	430	62
Total other liabilities	19,184	23,261
Derivatives, other | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Total other liabilities	0	0
Derivatives, other | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	260	62
Total other liabilities	369	466
Derivatives, other | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	170	0
Total other liabilities	18,815	22,795
U.S. treasuries | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	999,975	100
U.S. treasuries | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
U.S. treasuries | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	999,975	100
U.S. treasuries | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Government agency issued MBS | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	2,487,382	2,348,517
Government agency issued MBS | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Government agency issued MBS | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	2,487,382	2,348,517
Government agency issued MBS | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Government agency issued CMO | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	1,415,265	1,670,492
Government agency issued CMO | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Government agency issued CMO | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	1,415,265	1,670,492
Government agency issued CMO | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Other U.S. government agencies | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	417,292	306,092
Other U.S. government agencies | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Other U.S. government agencies | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	417,292	306,092
Other U.S. government agencies | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
States and municipalities | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	90,383	60,526
States and municipalities | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
States and municipalities | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	90,383	60,526
States and municipalities | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Corporates and other debt | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	40,413	40,540
Corporates and other debt | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Corporates and other debt | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	40,413	40,540
Corporates and other debt | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Equity, mutual funds, and other | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	22,692	22,643
Equity, mutual funds, and other | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	22,692	22,643
Equity, mutual funds, and other | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Equity, mutual funds, and other | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total other assets	0	0
Interest- only strips- AFS | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	25,446	19,136
Interest- only strips- AFS | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Interest- only strips- AFS | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	0	0
Interest- only strips- AFS | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Securities available-for-sale	25,446	19,136
Fixed Income | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	1,115,822	1,345,266
Total trading liabilities - fixed income	232,742	505,581
Fixed Income | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	1,115,822	1,345,266
Total trading liabilities - fixed income	232,742	505,581
Fixed Income | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | U.S. treasuries | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	119,121	134,844
Total trading liabilities - fixed income	195,753	406,380
Fixed Income | U.S. treasuries | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | U.S. treasuries | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	119,121	134,844
Total trading liabilities - fixed income	195,753	406,380
Fixed Income | U.S. treasuries | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | Government agency issued MBS | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	431,765	268,024
Total trading liabilities - fixed income		33
Fixed Income | Government agency issued MBS | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income		0
Fixed Income | Government agency issued MBS | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	431,765	268,024
Total trading liabilities - fixed income		33
Fixed Income | Government agency issued MBS | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income		0
Fixed Income | Government agency issued CMO | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	226,732	250,652
Fixed Income | Government agency issued CMO | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Fixed Income | Government agency issued CMO | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	226,732	250,652
Fixed Income | Government agency issued CMO | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Fixed Income | Other U.S. government agencies | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	91,203	124,972
Total trading liabilities - fixed income	578	88
Fixed Income | Other U.S. government agencies | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | Other U.S. government agencies | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	91,203	124,972
Total trading liabilities - fixed income	578	88
Fixed Income | Other U.S. government agencies | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | States and municipalities | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	17,467	120,744
Total trading liabilities - fixed income	756
Fixed Income | States and municipalities | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0
Fixed Income | States and municipalities | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	17,467	120,744
Total trading liabilities - fixed income	756
Fixed Income | States and municipalities | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0
Fixed Income | Corporates and other debt | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	229,556	445,253
Total trading liabilities - fixed income	35,655	99,080
Fixed Income | Corporates and other debt | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | Corporates and other debt | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	229,556	445,253
Total trading liabilities - fixed income	35,655	99,080
Fixed Income | Corporates and other debt | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Total trading liabilities - fixed income	0	0
Fixed Income | Equity, mutual funds, and other | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	(22)	777
Fixed Income | Equity, mutual funds, and other | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Fixed Income | Equity, mutual funds, and other | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	(22)	777
Fixed Income | Equity, mutual funds, and other | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Mortgage Banking | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	628	941
Mortgage Banking | Level 1 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Mortgage Banking | Level 2 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	0	0
Mortgage Banking | Level 3 | Recurring
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Trading securities	$ 628	$ 941