Fair Value Measurements Fair Value Recurring Basis (Details) - USD ($)	Dec. 31, 2017		Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 1,170,328,000		$ 1,264,132,000
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0		0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0		0
U.S. government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	34,299,000	[1]	39,936,000
Government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	302,501,000	[1]	336,664,000
Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	303,058,000	[1]	293,397,000
Mortgage-backed securities (1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	509,676,000	[2]	570,327,000	[3]
Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	20,794,000	[4]	23,808,000
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	0		0
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	1,170,328,000		1,264,132,000
Alternative Investment, Fair Value Disclosure	7,062,000		6,110,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	7,062,000		6,110,000
Fair Value, Measurements, Recurring [Member] | U.S. government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	34,299,000		39,936,000
Fair Value, Measurements, Recurring [Member] | Government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	302,501,000		336,664,000
Fair Value, Measurements, Recurring [Member] | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	303,058,000		293,397,000
Fair Value, Measurements, Recurring [Member] | Mortgage-backed securities (1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	509,676,000		570,327,000
Fair Value, Measurements, Recurring [Member] | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	20,794,000		23,808,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	54,890,000		63,101,000
Alternative Investment, Fair Value Disclosure	7,062,000		6,110,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	7,062,000		6,110,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	34,096,000		39,293,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed securities (1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	20,794,000		23,808,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	1,115,438,000		1,201,031,000
Alternative Investment, Fair Value Disclosure	0		0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	203,000		643,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	302,501,000		336,664,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	303,058,000		293,397,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed securities (1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	509,676,000		570,327,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Alternative Investment, Fair Value Disclosure	0		0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. government and agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Government-sponsored entities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Municipal bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed securities (1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0		0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	18,575,000		17,032,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	18,953,000		16,560,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	18,575,000		17,032,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	18,953,000		16,560,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Interest Rate Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Loan Participations and Assignments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1,000		15,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	108,000		6,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Loan Participations and Assignments [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Loan Participations and Assignments [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	1,000		15,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	108,000		6,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Loan Participations and Assignments [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0		0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	2,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	2,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	2,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	2,000
Fair Value, Measurements, Recurring [Member] | Not Designated as Hedging Instrument [Member] | Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	555,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	80,000		1,040,000
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0		0
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	555,000
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	80,000		1,040,000
Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	$ 0		$ 0

[1] Certain securities are callable before their final maturity.

[2] Mortgage-backed securities are shown based on their final (contractual) maturity, but, due to prepayments, they are expected to have shorter lives.

[3] All mortgage-backed securities are guaranteed by U.S. government agencies or Government-sponsored entities.

[4] Other securities consist of money market mutual funds and equity securities held by certain Wealth Advisory and Investment Management businesses.