Investment Securities (Schedule of Investment Securities Portfolio Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	$ 168,705	$ 250,113
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(3,229)	(2,012)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	1,476,248	1,292,730
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(62,964)	(34,015)
Available-for-sale, continuous unrealized loss position, Fair value	1,644,953	1,542,843
Available-for-sale, continuous unrealized loss position, Unrealized losses	(66,193)	(36,027)
Held-to-maturity securities
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	38,239	298,750
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	(637)	(4,267)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	759,540	352,599
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(32,947)	(12,357)
Held-to-maturity securities, continuous unrealized loss position, Fair value	797,779	651,349
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(33,584)	(16,624)
U.S. Treasury
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	5,485	24,811
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(5)	(215)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	24,829	119,011
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(181)	(867)
Available-for-sale, continuous unrealized loss position, Fair value	30,314	143,822
Available-for-sale, continuous unrealized loss position, Unrealized losses	(186)	(1,082)
U.S. Government agencies
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	0	14,462
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	0	(69)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	11,167	141,471
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(30)	(656)
Available-for-sale, continuous unrealized loss position, Fair value	11,167	155,933
Available-for-sale, continuous unrealized loss position, Unrealized losses	(30)	(725)
Held-to-maturity securities
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	0	241,849
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	0	(3,263)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	601,238	300,200
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(28,576)	(10,803)
Held-to-maturity securities, continuous unrealized loss position, Fair value	601,238	542,049
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(28,576)	(14,066)
Municipal
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	10,676	28,221
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(178)	(256)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	22,147	15,840
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(590)	(301)
Available-for-sale, continuous unrealized loss position, Fair value	32,823	44,061
Available-for-sale, continuous unrealized loss position, Unrealized losses	(768)	(557)
Held-to-maturity securities
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	38,239	56,901
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	(637)	(1,004)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	158,302	52,399
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(4,371)	(1,554)
Held-to-maturity securities, continuous unrealized loss position, Fair value	196,541	109,300
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(5,008)	(2,558)
Corporate notes, financial issuers
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	37,076	1,210
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(2,921)	(1)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	42,934	5,665
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(4,148)	(300)
Available-for-sale, continuous unrealized loss position, Fair value	80,010	6,875
Available-for-sale, continuous unrealized loss position, Unrealized losses	(7,069)	(301)
Corporate notes, other
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	0	0
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	0	0
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	0	999
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(1)
Available-for-sale, continuous unrealized loss position, Fair value	0	999
Available-for-sale, continuous unrealized loss position, Unrealized losses	0	(1)
Mortgage-backed securities
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	114,958	137,255
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(124)	(915)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	1,340,916	989,971
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(57,193)	(31,040)
Available-for-sale, continuous unrealized loss position, Fair value	1,455,874	1,127,226
Available-for-sale, continuous unrealized loss position, Unrealized losses	(57,317)	(31,955)
Collateralized mortgage obligations
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	510	35,038
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(1)	(213)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	34,255	13,719
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(822)	(404)
Available-for-sale, continuous unrealized loss position, Fair value	34,765	48,757
Available-for-sale, continuous unrealized loss position, Unrealized losses	$ (823)	(617)
Equity securities with readily determinable fair value
Available-for-sale securities
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value		9,116
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses		(343)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value		6,054
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses		(446)
Available-for-sale, continuous unrealized loss position, Fair value		15,170
Available-for-sale, continuous unrealized loss position, Unrealized losses		$ (789)