Derivatives (Fair Values of Derivative Financial Instruments) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		$ 2,740,984	$ 2,342,791
Fair Values, Assets		1,329	4,788
Fair Values, Liabilities		5,567	26,846
Less: Netting Adjustment, Assets	[1],[2]	(2,780)
Less: Netting Adjustment, Liabilities	[1],[2]	(16,747)
Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		1,238,000	1,100,000
Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		1,502,984	1,242,791
Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	[3]	1,172,752	979,391
Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		109,556	84,732
Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		93,809	75,676
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		71,786	46,840
Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount		55,081	56,152
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	19,979	20,315
Total derivative assets/liabilities	[1]	17,199	20,315
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	19,979	20,315
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1],[3]	16,855	18,405
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	34	50
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	91	900
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	534	189
Other Assets [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Assets	[1]	2,465	771
Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	29,438	27,432
Total derivative assets/liabilities	[1]	12,691	27,432
Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	8,747	7,787
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	20,691	19,645
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1],[3]	17,420	18,362
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Risk Participation Agreements [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	108	105
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Forward Commitments to Sell Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	669	221
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Interest Rate-Lock Commitments on Residential Mortgage Loans [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	71	228
Other Liabilities [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Foreign Exchange Forward Contracts [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	2,423	729
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
Cash Flow Hedge [Member] | Other Liabilities [Member] | Derivatives Designated as Hedging Instruments [Member] | Interest Rate Swaps [Member]
Derivatives, Fair Value [Line Items]
Fair Values, Liabilities	[1]	7,924	$ 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		363,000
Fair Values, Liabilities	[1]	$ 823

[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.