Derivatives and Hedging Activities (Customer Related Derivative Positions - Not Designated as Hedges) (Details) $ in Thousands		Mar. 31, 2018 USD ($) position	Dec. 31, 2017 USD ($) position
Summary of customer related derivative positions, not designated as hedging
Fair Value		$ 1,974	$ 1,616
Not Designated as Hedging Instrument | Receive fixed, pay variable | Loan level swaps
Summary of customer related derivative positions, not designated as hedging
Number of Positions | position	[1]	248	246
Less than 1 year		$ 34,081	$ 36,023
Less than 2 years		95,894	61,500
Less than 3 years		173,172	152,287
Less than 4 years		59,531	111,147
Thereafter		602,621	591,385
Total		965,299	952,342
Fair Value		$ (11,404)	$ 3,875
Not Designated as Hedging Instrument | Pay fixed, receive variable | Loan level swaps
Summary of customer related derivative positions, not designated as hedging
Number of Positions | position	[1]	233	231
Less than 1 year		$ 34,081	$ 36,023
Less than 2 years		95,894	61,500
Less than 3 years		173,172	152,287
Less than 4 years		59,531	111,147
Thereafter		602,621	591,385
Total		965,299	952,342
Fair Value		$ 11,390	$ (3,880)
Not Designated as Hedging Instrument | Buys foreign currency, sells U.S. currency | Foreign exchange contracts
Summary of customer related derivative positions, not designated as hedging
Number of Positions | position	[1]	18	15
Less than 1 year		$ 33,089	$ 26,382
Less than 2 years			3,780
Total		33,089	30,162
Fair Value		$ 770	$ 1,202
Not Designated as Hedging Instrument | Buys U.S. currency, sells foreign currency | Foreign exchange contracts
Summary of customer related derivative positions, not designated as hedging
Number of Positions | position	[1]	18	15
Less than 1 year		$ 33,089	$ 26,382
Less than 2 years			3,780
Total		33,089	30,162
Fair Value		$ (751)	$ (1,188)

[1] The Company may enter into one dealer swap agreement which offsets multiple commercial borrower swap agreements.