Derivatives and Hedging Activities (Interest Rate Contract Derivative Financial Instruments and Related Hedged Items) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivatives Fair Value [Line Items]
Notional amount of interest rate swap derivatives	$ 3,104,736	$ 2,297,502
Interest rate derivative assets, fair value	29,765	21,831
Interest rate derivative liabilities, fair value	(69,177)	(43,788)
Derivatives designated as cash flow hedges | Pay-Fixed interest Rate Swaps - CDs
Derivatives Fair Value [Line Items]
Weighted average fixed rate of interest rate swaps (in Percent)	3.11%	3.11%
Description of variable rate (in Description)	12-Month Libor	12-Month Libor
Weighted average remaining maturity of interest rate swap derivatives (in Duration)	0 years 10 months 6 days	1 year 10 months 24 days
Notional amount of interest rate swap derivatives	225,000	225,000
Derivatives designated as cash flow hedges | Pay-Fixed interest Rate Swaps - CDs | Other Liabilities
Derivatives Fair Value [Line Items]
Interest rate derivative liabilities, fair value	(5,741)	(10,591)
Derivatives designated as cash flow hedges | Pay-Fixed interest rate swaps - Borrowings
Derivatives Fair Value [Line Items]
Weighted average fixed rate of interest rate swaps (in Percent)	1.61%	1.61%
Description of variable rate (in Description)	3-Month Libor	3-Month Libor
Weighted average remaining maturity of interest rate swap derivatives (in Duration)	2 years 10 months 1 day	3 years 9 months 18 days
Notional amount of interest rate swap derivatives	1,505,000	1,505,000
Derivatives designated as cash flow hedges | Pay-Fixed interest rate swaps - Borrowings | Other Liabilities
Derivatives Fair Value [Line Items]
Interest rate derivative liabilities, fair value	(19,639)	(28,326)
Derivatives designated as cash flow hedges | Pay-Fixed interest rate swaps - Borrowings | Other Assets
Derivatives Fair Value [Line Items]
Interest rate derivative assets, fair value	4,083	16,960
Derivatives designated as cash flow hedges | Pay-Fixed Forward-Starting Swap - Borrowings
Derivatives Fair Value [Line Items]
Weighted average fixed rate of interest rate swaps (in Percent)	3.43%
Description of variable rate (in Description)	3-Month Libor
Weighted average remaining maturity of interest rate swap derivatives (in Duration)	12 years 5 months 16 days
Notional amount of interest rate swap derivatives	300,000
Derivatives designated as cash flow hedges | Pay-Fixed Forward-Starting Swap - Borrowings | Other Liabilities
Derivatives Fair Value [Line Items]
Interest rate derivative liabilities, fair value	(18,115)
Derivatives not designated as hedges | Pay-fixed interest rate swaps and caps
Derivatives Fair Value [Line Items]
Weighted average fixed rate of interest rate swaps (in Percent)	4.34%	4.62%
Description of variable rate (in Description)	Indexed to 1-month Libor	Indexed to 1-month Libor
Weighted average remaining maturity of interest rate swap derivatives (in Duration)	6 years 4 months 6 days	6 years 4 months 24 days
Notional amount of interest rate swap derivatives	537,368	283,751
Derivatives not designated as hedges | Pay-fixed interest rate swaps and caps | Other Liabilities
Derivatives Fair Value [Line Items]
Interest rate derivative liabilities, fair value	(25,622)	(3,816)
Derivatives not designated as hedges | Pay-fixed interest rate swaps and caps | Other Assets
Derivatives Fair Value [Line Items]
Interest rate derivative assets, fair value	60	1,055
Derivatives not designated as hedges | Pay-variable interest rate swaps and caps
Derivatives Fair Value [Line Items]
Weighted average fixed rate of interest rate swaps (in Percent)	4.34%	4.62%
Description of variable rate (in Description)	Indexed to 1-month Libor	Indexed to 1-month Libor
Weighted average remaining maturity of interest rate swap derivatives (in Duration)	6 years 4 months 6 days	6 years 4 months 24 days
Notional amount of interest rate swap derivatives	537,368	283,751
Derivatives not designated as hedges | Pay-variable interest rate swaps and caps | Other Liabilities
Derivatives Fair Value [Line Items]
Interest rate derivative liabilities, fair value	(60)	(1,055)
Derivatives not designated as hedges | Pay-variable interest rate swaps and caps | Other Assets
Derivatives Fair Value [Line Items]
Interest rate derivative assets, fair value	$ 25,622	$ 3,816