Investment Securities (Contractual Maturities of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, due in one year or less, Amortized Cost	$ 145,353	$ 160,856
Available-for-sale securities, due in one year or less, Fair Value	145,062	160,756
Available-for-sale securities, due in one to five years, Amortized Cost	321,019	166,550
Available-for-sale securities, due in one to five years, Fair Value	320,423	166,468
Available-for-sale securities, due in five to ten years, Amortized Cost	27,319	228,652
Available-for-sale securities, due in five to ten years, Fair Value	28,451	225,699
Available-for-sale securities, due after ten years, Amortized Cost	34,296	13,753
Available-for-sale securities, due after ten years, Fair Value	34,399	14,182
Available-for-sale securities, Amortized Cost Basis	1,776,148	1,731,292
Available-for-sale securities, at fair value	1,724,667	1,716,388
Held-to-maturity securities, due in one year or less, Amortized Cost	0	0
Held-to-maturity securities, due in one year or less, Fair Value	0	0
Held-to-maturity securities, due in one to five years, Amortized Cost	29,794	19,208
Held-to-maturity securities, due in one to five years, Fair Value	29,416	19,156
Held-to-maturity securities, due in five to ten years, Amortized Cost	69,664	96,454
Held-to-maturity securities, due in five to ten years, Fair Value	67,820	96,091
Held-to-maturity securities, due after ten years, Amortized Cost	536,247	769,164
Held-to-maturity securities, due after ten years, Fair Value	510,366	762,864
Held-to-maturity securities	635,705	884,826
Held-to-maturity Securities, Fair Value	607,602	878,111
Mortgage-backed
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	1,215,553	1,110,101
Available-for-sale securities, at fair value	1,161,084	1,092,597
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, Amortized Cost Basis	32,608	51,380
Available-for-sale securities, at fair value	$ 35,248	$ 56,686