Investment Securities (Schedule of Investment Securities Portfolio Continuous Unrealized Loss Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	$ 1,430,852	$ 1,257,582
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(56,387)	(22,293)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	57,074	185,788
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(2,023)	(7,377)
Available-for-sale, continuous unrealized loss position, Fair value	1,487,926	1,443,370
Available-for-sale, continuous unrealized loss position, Unrealized losses	(58,410)	(29,670)
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	526,328	502,733
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	(27,387)	(4,505)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	55,741	264,710
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(1,370)	(3,081)
Held-to-maturity securities, continuous unrealized loss position, Fair value	582,069	767,443
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(28,757)	(7,586)
U.S. Treasury
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	133,980	306,729
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(759)	(5,553)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	0	0
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	0
Available-for-sale, continuous unrealized loss position, Fair value	133,980	306,729
Available-for-sale, continuous unrealized loss position, Unrealized losses	(759)	(5,553)
US Government agencies
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	89,645	56,193
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(435)	(192)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	0	8,434
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(83)
Available-for-sale, continuous unrealized loss position, Fair value	89,645	64,627
Available-for-sale, continuous unrealized loss position, Unrealized losses	(435)	(275)
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	355,621	450,800
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	(23,250)	(4,223)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	50,033	235,518
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(1,220)	(2,921)
Held-to-maturity securities, continuous unrealized loss position, Fair value	405,654	686,318
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(24,470)	(7,144)
Municipal
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	54,711	24,673
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(408)	(261)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	6,684	3,680
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(198)	(95)
Available-for-sale, continuous unrealized loss position, Fair value	61,395	28,353
Available-for-sale, continuous unrealized loss position, Unrealized losses	(606)	(356)
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Fair value	170,707	51,933
Held-to-maturity securities, continuous unrealized loss position, less than 12 months, Unrealized loss	(4,137)	(282)
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Fair value	5,708	29,192
Held-to-maturity securities, continuous unrealized loss position, 12 months or longer, Unrealized loss	(150)	(160)
Held-to-maturity securities, continuous unrealized loss position, Fair value	176,415	81,125
Held-to-maturity securities, continuous unrealized loss position, Unrealized loss	(4,287)	(442)
Corporate notes, financial issuers
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	13,157	16,225
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(11)	(266)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	34,972	34,744
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(989)	(1,215)
Available-for-sale, continuous unrealized loss position, Fair value	48,129	50,969
Available-for-sale, continuous unrealized loss position, Unrealized losses	(1,000)	(1,481)
Corporate notes, other
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	999	998
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(1)	(2)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	0	0
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	0
Available-for-sale, continuous unrealized loss position, Fair value	999	998
Available-for-sale, continuous unrealized loss position, Unrealized losses	(1)	(2)
Mortgage-backed securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	1,116,705	835,086
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(54,330)	(15,753)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	0	121,249
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	0	(5,251)
Available-for-sale, continuous unrealized loss position, Fair value	1,116,705	956,335
Available-for-sale, continuous unrealized loss position, Unrealized losses	(54,330)	(21,004)
Mortgage-backed, collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	15,038	12,782
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(229)	(189)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	6,905	9,196
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(261)	(317)
Available-for-sale, continuous unrealized loss position, Fair value	21,943	21,978
Available-for-sale, continuous unrealized loss position, Unrealized losses	(490)	(506)
Equity securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, continuous unrealized losses existing for less than 12 months, Fair value	6,617	4,896
Available-for-sale, continuous unrealized losses existing for less than 12 months, Unrealized losses	(214)	(77)
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Fair value	8,513	8,485
Available-for-sale, continuous unrealized losses existing for greater than 12 months, Unrealized losses	(575)	(416)
Available-for-sale, continuous unrealized loss position, Fair value	15,130	13,381
Available-for-sale, continuous unrealized loss position, Unrealized losses	$ (789)	$ (493)