Securities (Schedule of Contractual Maturities of Investment Securities Available for Sale) (Details) $ in Thousands	Sep. 30, 2015 USD ($)
Available-for-sale Securities [Abstract]
Due within one year, Amortized Cost	$ 22,054
Due after one year through five years, Amortized Cost	418,087
Due after five years through ten years, Amortized Cost	543,698
Due after ten years, Amortized Cost	1,015,605
No stated maturity date, Amortized Cost Basis	5,284
Total investment securities available-for-sale, Amortized Cost	2,004,728
Due within one year, Fair Value	22,320
Due after one year through five years, Fair Value	421,722
Due after five years through ten years, Fair Value	553,422
Due after ten years, Fair Value	1,024,793
No stated maturity date, Fair Value	5,167
Total investment securities available-for-sale, Fair Value	$ 2,027,424