Derivatives (Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2019	Dec. 31, 2018
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		$ 3,989,850	$ 3,024,565
Fair Values, Assets		24	3,325
Less: netting adjustment, Assets	[1],[2]	(31,598)	(11,979)
Fair Values, Liabilities		14,620	2,160
Less: netting adjustment, Liabilities	[1],[2]	(65,088)	(22,588)
Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	103,502	28,959
Total derivative assets/liabilities	[1]	71,904	16,980
Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Total derivative assets/liabilities	[1]	23,467	22,227
Fair Values, Liabilities	[1]	88,555	44,815
Derivatives Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		1,679,510	1,358,110
Derivatives Designated as Hedging Instruments [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	31,453	3,954
Derivatives Designated as Hedging Instruments [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	7,952	11,262
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		2,310,340	1,666,455
Derivatives Not Designated as Hedging Instruments [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	72,049	25,005
Derivatives Not Designated as Hedging Instruments [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	80,603	33,553
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount	[3]	1,726,248	1,277,404
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1],[3]	70,701	23,670
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1],[3]	72,804	24,669
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		237,081	171,222
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	38	10
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	60	131
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		151,413	77,208
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]	335	110
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]	649	664
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		78,769	59,119
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]	240	464
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]	149	67
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		73,076	37,749
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Fair Values, Assets	[1]	735	751
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	692	718
Derivatives Not Designated as Hedging Instruments [Member] | Visa Class B derivative contract [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		43,753	43,753
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]	6,249	7,304
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		1,075,000	875,000
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]	31,453	3,954
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]		9,173
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Securities [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		441,400
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]	7,872
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Brokered Deposits [Member]
Derivatives Fair Value [Line Items]
Notional or Contractual Amount		163,110	483,110
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps - Brokered Deposits [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Fair Values, Liabilities	[1]	$ 80	$ 2,089

[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.

[3] The notional amount represents both the customer accommodation agreements and offsetting agreements with unrelated financial institutions