Securities (Schedule of Contractual Maturities of Investment Securities Available for Sale) (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Available-for-sale Securities [Abstract]
Due within one year, Amortized Cost	$ 28,765
Due after one year through five years, Amortized Cost	484,206
Due after five years through ten years, Amortized Cost	688,715
Due after ten years, Amortized Cost	1,117,751
No stated maturity date, Amortized Cost Basis	5,284
Total investment securities available-for-sale, Amortized Cost	2,324,721
Due within one year, Fair Value	28,874
Due after one year through five years, Fair Value	493,479
Due after five years through ten years, Fair Value	703,388
Due after ten years, Fair Value	1,129,141
No stated maturity date, Fair Value	5,202
Total investment securities available-for-sale, Fair Value	$ 2,360,084