Investment Securities (Summary Of Gross Unrealized Losses Not Considered OTTI) (Detail) $ in Thousands	Sep. 30, 2017 USD ($) holding	Dec. 31, 2016 USD ($) holding
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$ 986,229	$ 1,236,547
Available for sale, Unrealized Losses - Less Than Twelve Months	(12,877)	(27,316)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	659,271	470,314
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (19,114)	$ (13,582)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	169	168
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 1,645,500	$ 1,706,861
Available for sale, Unrealized Losses - Total	(31,991)	(40,898)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,688,111	2,351,350
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(14,274)	(63,785)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,089,959	292,225
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (35,664)	$ (9,315)
Held-to-maturity, Number of Holdings - Total | holding	366	395
Held-to-maturity, Fair Value - Total	$ 2,778,070	$ 2,643,575
Held-to-maturity, Unrealized Losses - Total	(49,938)	(73,100)
Agency CMO [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	75,042	107,853
Available for sale, Unrealized Losses - Less Than Twelve Months	(1,002)	(2,168)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	70,167	67,351
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (2,114)	$ (1,335)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	16	15
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 145,209	$ 175,204
Available for sale, Unrealized Losses - Total	(3,116)	(3,503)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	82,839	163,439
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(880)	(3,339)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	83,103	17,254
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (2,150)	$ (485)
Held-to-maturity, Number of Holdings - Total | holding	19	16
Held-to-maturity, Fair Value - Total	$ 165,942	$ 180,693
Held-to-maturity, Unrealized Losses - Total	(3,030)	(3,824)
Agency MBS [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	464,031	512,075
Available for sale, Unrealized Losses - Less Than Twelve Months	(5,169)	(10,503)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	303,770	252,779
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (8,887)	$ (9,006)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	104	97
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 767,801	$ 764,854
Available for sale, Unrealized Losses - Total	(14,056)	(19,509)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	870,376	1,394,623
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(7,948)	(32,942)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	775,331	273,779
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (22,064)	$ (8,826)
Held-to-maturity, Number of Holdings - Total | holding	157	150
Held-to-maturity, Fair Value - Total	$ 1,645,707	$ 1,668,402
Held-to-maturity, Unrealized Losses - Total	(30,012)	(41,768)
Agency CMBS [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	306,025	554,246
Available for sale, Unrealized Losses - Less Than Twelve Months	(6,240)	$ (14,567)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	278,935
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (7,965)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	34	32
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 584,960	$ 554,246
Available for sale, Unrealized Losses - Total	(14,205)	(14,567)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	570,781	347,725
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(3,504)	$ (1,348)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,730
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (45)
Held-to-maturity, Number of Holdings - Total | holding	45	25
Held-to-maturity, Fair Value - Total	$ 575,511	$ 347,725
Held-to-maturity, Unrealized Losses - Total	(3,549)	(1,348)
Non-agency CMBS [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	39,775	12,427
Available for sale, Unrealized Losses - Less Than Twelve Months	$ (121)	(24)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		63,930
Available for sale, Unrealized Losses - Twelve Months or Longer		$ (678)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	5	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 39,775	$ 76,357
Available for sale, Unrealized Losses - Total	(121)	(702)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	40,150	60,768
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(197)	$ (411)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	$ 250
Held-to-maturity, Number of Holdings - Total | holding	5	8
Held-to-maturity, Fair Value - Total	$ 40,400	$ 60,768
Held-to-maturity, Unrealized Losses - Total	(197)	(411)
CLO [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	82,989	49,946
Available for sale, Unrealized Losses - Less Than Twelve Months	$ (161)	(54)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value		50,237
Available for sale, Unrealized Losses - Twelve Months or Longer		$ (465)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	5	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 82,989	$ 100,183
Available for sale, Unrealized Losses - Total	(161)	(519)
Single issuer trust preferred securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	12,570	0
Available for sale, Unrealized Losses - Less Than Twelve Months	(97)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,574	28,633
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (105)	$ (1,748)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	3	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 17,144	$ 28,633
Available for sale, Unrealized Losses - Total	(202)	(1,748)
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	5,797
Available for sale, Unrealized Losses - Less Than Twelve Months	(87)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,825	7,384
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (43)	$ (350)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	2	2
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 7,622	$ 7,384
Available for sale, Unrealized Losses - Total	(130)	(350)
Municipal bonds and notes [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	123,965	384,795
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(1,745)	(25,745)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	226,545	1,192
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (11,405)	$ (4)
Held-to-maturity, Number of Holdings - Total | holding	140	196
Held-to-maturity, Fair Value - Total	$ 350,510	$ 385,987
Held-to-maturity, Unrealized Losses - Total	$ (13,150)	$ (25,749)