Investment Securities (Contractual Maturities of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities, due in one year or less, Amortized Cost	$ 160,856	$ 285,596
Available-for-sale securities, due in one year or less, Fair Value	160,756	285,889
Available-for-sale securities, due in one to five years, Amortized Cost	166,550	172,647
Available-for-sale securities, due in one to five years, Fair Value	166,468	172,885
Available-for-sale securities, due in five to ten years, Amortized Cost	228,652	331,389
Available-for-sale securities, due in five to ten years, Fair Value	225,699	325,644
Available-for-sale securities, due after ten years, Amortized Cost	13,753	653,213
Available-for-sale securities, due after ten years, Fair Value	14,182	637,811
Total available-for-sale securities, Amortized Cost	1,731,292	1,807,913
Available-for-sale securities, at fair value	1,716,388	1,792,078
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	19,208	0
Held-to-maturity securities, due in one to five years, Fair Value	19,156	0
Held-to-maturity securities, due in five to ten years, Amortized Cost	96,454	0
Held-to-maturity securities, due in five to ten years, Fair Value	96,091	0
Held-to-maturity securities, due after ten years, Amortized Cost	769,164	0
Held-to-maturity securities, due after ten years, Fair Value	762,864	0
Held-to-maturity securities	884,826	0
Held-to-maturity Securities, Fair Value	878,111	0
Mortgage-backed
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	1,110,101	318,476
Available-for-sale securities, at fair value	1,092,597	318,710
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Total available-for-sale securities, Amortized Cost	51,380	46,592
Available-for-sale securities, at fair value	$ 56,686	$ 51,139