Investment Securities (Summary Of Gross Unrealized Losses Not Considered OTTI) (Detail) $ in Thousands	Sep. 30, 2019 USD ($) holding	Dec. 31, 2018 USD ($) holding
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 141,685	$ 799,954
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,275)	(8,602)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	968,616	1,756,617
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (11,948)	$ (90,067)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	141	309
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,110,301	$ 2,556,571
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(13,223)	(98,669)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	375,714	382,558
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(2,864)	(3,069)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	921,412	3,257,871
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (10,687)	$ (125,132)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	137	596
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 1,297,126	$ 3,640,429
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(13,551)	(128,201)
Agency CMO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18,109	15,524
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(146)	(72)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	35,751	180,641
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (519)	$ (4,385)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	11	36
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 53,860	$ 196,165
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(665)	(4,457)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	15,744	691
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(40)	(1)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	58,852	182,396
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (640)	$ (5,254)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	8	25
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 74,596	$ 183,087
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(680)	(5,255)
Agency MBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	47,966	321,678
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(33)	(2,078)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	419,082	975,084
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (5,045)	$ (39,998)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	85	184
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 467,048	$ 1,296,762
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(5,078)	(42,076)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	183,181	288,635
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,219)	(1,916)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	858,373	1,892,951
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (10,030)	$ (77,785)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	119	272
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 1,041,554	$ 2,181,586
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(11,249)	(79,701)
Agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	461,840	566,237
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (2,814)	$ (41,930)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	28	37
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 461,840	$ 566,237
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(2,814)	(41,930)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	127,662
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,552)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	4,187	635,284
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (17)	$ (22,572)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	6	56
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 131,849	$ 635,284
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(1,569)	(22,572)
Non-agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	49,418	343,457
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(35)	(2,937)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,489	5,193
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (11)	$ (24)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	8	39
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 52,907	$ 348,650
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(46)	(2,961)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	46,610	24,881
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (36)	(270)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		132,464
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ (2,118)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	3	20
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 46,610	$ 157,345
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(36)	(2,388)
CLO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18,405	83,305
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(294)	(1,695)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	24,927	14,873
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (73)	$ (269)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	2	5
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 43,332	$ 98,178
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(367)	(1,964)
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	7,787	35,990
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(767)	(1,820)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	23,527	14,589
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (3,486)	$ (3,461)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	7	8
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 31,314	$ 50,579
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(4,253)	(5,281)
Municipal bonds and notes [Member]
Schedule of Investments [Line Items]
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	2,517	68,351
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (17)	(882)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value		414,776
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ (17,403)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	1	223
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 2,517	$ 483,127
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ (17)	$ (18,285)