Investment Securities (Schedule of Investment Securities Portfolio Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	$ 1,050,089	$ 168,705
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(10,824)	(3,229)
Continuous unrealized losses existing for greater than 12 months, Fair value	4,115	1,476,248
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(253)	(62,964)
Total, Fair value	1,054,204	1,644,953
Total, Unrealized losses	(11,077)	(66,193)
Held-to-maturity securities
Continuous unrealized losses existing for less than 12 months, Fair value	49,941	38,239
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(5,699)	(637)
Continuous unrealized losses existing for greater than 12 months, Fair value	0	759,540
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(32,947)
Total, Fair value	49,941	797,779
Total, Unrealized losses	(5,699)	(33,584)
U.S. Treasury
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	0	5,485
Continuous unrealized losses existing for less than 12 months, Unrealized losses	0	(5)
Continuous unrealized losses existing for greater than 12 months, Fair value	0	24,829
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(181)
Total, Fair value	0	30,314
Total, Unrealized losses	0	(186)
U.S. Government agencies
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	193,533	0
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(3,754)	0
Continuous unrealized losses existing for greater than 12 months, Fair value	0	11,167
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(30)
Total, Fair value	193,533	11,167
Total, Unrealized losses	(3,754)	(30)
Held-to-maturity securities
Continuous unrealized losses existing for less than 12 months, Fair value	40,144	0
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(5,460)	0
Continuous unrealized losses existing for greater than 12 months, Fair value	0	601,238
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(28,576)
Total, Fair value	40,144	601,238
Total, Unrealized losses	(5,460)	(28,576)
Municipal
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	28,246	10,676
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(165)	(178)
Continuous unrealized losses existing for greater than 12 months, Fair value	52	22,147
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(3)	(590)
Total, Fair value	28,298	32,823
Total, Unrealized losses	(168)	(768)
Held-to-maturity securities
Continuous unrealized losses existing for less than 12 months, Fair value	9,797	38,239
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(239)	(637)
Continuous unrealized losses existing for greater than 12 months, Fair value	0	158,302
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(4,371)
Total, Fair value	9,797	196,541
Total, Unrealized losses	(239)	(5,008)
Corporate notes, financial issuers
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	67,838	37,076
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(3,760)	(2,921)
Continuous unrealized losses existing for greater than 12 months, Fair value	2,758	42,934
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(242)	(4,148)
Total, Fair value	70,596	80,010
Total, Unrealized losses	(4,002)	(7,069)
Corporate notes, other
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	0	0
Continuous unrealized losses existing for less than 12 months, Unrealized losses	0	0
Continuous unrealized losses existing for greater than 12 months, Fair value	0	0
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	0
Total, Fair value	0	0
Total, Unrealized losses	0	0
Mortgage-backed securities
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	751,053	114,958
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(3,013)	(124)
Continuous unrealized losses existing for greater than 12 months, Fair value	0	1,340,916
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(57,193)
Total, Fair value	751,053	1,455,874
Total, Unrealized losses	(3,013)	(57,317)
Collateralized mortgage obligations
Available-for-sale securities
Continuous unrealized losses existing for less than 12 months, Fair value	9,419	510
Continuous unrealized losses existing for less than 12 months, Unrealized losses	(132)	(1)
Continuous unrealized losses existing for greater than 12 months, Fair value	1,305	34,255
Continuous unrealized losses existing for greater than 12 months, Unrealized losses	(8)	(822)
Total, Fair value	10,724	34,765
Total, Unrealized losses	$ (140)	$ (823)