Derivatives (Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		$ 2,799,296	$ 2,342,791
Fair Values, Assets		2,148	4,788
Fair Values, Liabilities		3,938	26,846
Less: netting adjustment, Assets	[1],[2]	(4,913)
Less: netting adjustment, Liabilities	[1],[2]	(21,563)
Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		1,358,110	1,100,000
Fair Values, Liabilities	[1]	16,495	7,787
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		1,441,186	1,242,791
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	[3]	1,144,789	979,391
Fair Values, Assets	[1],[3]	15,408	18,405
Fair Values, Liabilities	[1],[3]	15,857	18,362
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		119,951	84,732
Fair Values, Assets	[1]	23	50
Fair Values, Liabilities	[1]	109	105
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		80,462	75,676
Fair Values, Assets	[1]	1,000	900
Fair Values, Liabilities	[1]	290	221
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		53,724	46,840
Fair Values, Assets	[1]	186	189
Fair Values, Liabilities	[1]	782	228
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		42,260	56,152
Fair Values, Assets	[1]	2,453	771
Fair Values, Liabilities	[1]	2,419	729
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	19,070	20,315
Total derivative assets/liabilities	[1]	14,157	20,315
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	19,070	20,315
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	35,952	27,432
Total derivative assets/liabilities	[1]	14,389	27,432
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	19,457	19,645
Cash Flow Hedge [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		875,000	1,100,000
Fair Values, Liabilities	[1]	14,020	$ 7,787
Fair Value Hedging [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		483,110
Fair Values, Liabilities	[1]	$ 2,475

[1] Derivative assets and liabilities are reported with 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.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.