Derivatives (Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2021	Dec. 31, 2020
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		$ 8,867,579	$ 7,975,022
Fair Values, Assets		4,691	2,869
Less: netting adjustment, Assets	[1],[2]	(65,844)	(57,648)
Fair Values, Liabilities		32,997	44,841
Less: netting adjustment, Liabilities	[1],[2]	(79,763)	(124,204)
Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	175,297	207,828
Total derivative assets/liabilities	[1]	109,453	150,180
Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Total derivative assets/liabilities	[1]	44,318	55,257
Fair Values, Liabilities	[1]	124,081	179,461
Derivatives Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		3,133,150	2,333,150
Derivatives Designated as Hedging Instruments [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	64,502	57,648
Derivatives Designated as Hedging Instruments [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	9,594	18,920
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		5,734,429	5,641,872
Derivatives Not Designated as Hedging Instruments [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	110,795	150,180
Derivatives Not Designated as Hedging Instruments [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	114,487	160,541
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		5,140,896	4,806,258
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	105,531	145,517
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	105,845	148,778
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		200,477	216,511
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	14	35
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	34	108
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		73,205	310,458
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]		19
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	1,764	3,211
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		130,004	206,258
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	3,273	1,793
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]		14
Derivatives Not Designated as Hedging Instruments [Member] | To Be Announced (TBA) Securities [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		82,500
Derivatives Not Designated as Hedging Instruments [Member] | To Be Announced (TBA) Securities [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	39
Derivatives Not Designated as Hedging Instruments [Member] | To Be Announced (TBA) Securities [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	151
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		63,782	58,822
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	1,938	2,816
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	1,826	2,785
Derivatives Not Designated as Hedging Instruments [Member] | Visa Class B derivative contract [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		43,565	43,565
Derivatives Not Designated as Hedging Instruments [Member] | Visa Class B derivative contract [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	4,867	5,645
Cash Flow Hedge [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Variable Rate Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		1,525,000	1,175,000
Cash Flow Hedge [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Variable Rate Loans [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	38,643	50,962
Cash Flow Hedge [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Variable Rate Loans [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	420
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Securities [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		1,608,150	1,158,150
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Securities [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	25,859	6,686
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Securities [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	$ 9,174	$ 18,920

[1] Derivative assets and liabilities are reported at fair value in other assets or other liabilities, respectively, in the consolidated balance sheets.

[2] Represents balance sheet netting of derivative assets and liabilities for variation margin collateral held or placed with the same central clearing counterparty. See offsetting assets and liabilities for further information.