Investment Securities (Summary Of Gross Unrealized Losses Not Considered OTTI) (Detail) $ in Thousands	Jun. 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	$ 71,812	$ 799,954
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,204)	(8,602)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,439,632	1,756,617
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (32,988)	$ (90,067)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	187	309
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 1,511,444	$ 2,556,571
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(34,192)	(98,669)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	3,560	382,558
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3)	(3,069)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,975,874	3,257,871
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (26,391)	$ (125,132)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	251	596
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 1,979,434	$ 3,640,429
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(26,394)	(128,201)
Agency CMO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	6	15,524
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(72)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	83,924	180,641
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (1,264)	$ (4,385)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	11	36
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 83,930	$ 196,165
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(1,264)	(4,457)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	210	691
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	(1)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	84,453	182,396
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (1,406)	$ (5,254)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	11	25
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 84,663	$ 183,087
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(1,406)	(5,255)
Agency MBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		321,678
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(2,078)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	748,498	975,084
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (11,665)	$ (39,998)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	123	184
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 748,498	$ 1,296,762
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(11,665)	(42,076)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value		288,635
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(1,916)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	1,268,211	1,892,951
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (20,616)	$ (77,785)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	166	272
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 1,268,211	$ 2,181,586
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(20,616)	(79,701)
Agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	542,244	566,237
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (16,022)	$ (41,930)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	34	37
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 542,244	$ 566,237
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(16,022)	(41,930)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	536,755	635,284
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (3,684)	$ (22,572)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	44	56
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 536,755	$ 635,284
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(3,684)	(22,572)
Non-agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	45,740	343,457
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(22)	(2,937)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	17,000	5,193
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (1)	$ (24)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	10	39
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 62,740	$ 348,650
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(23)	(2,961)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Fair Value	3,350	24,881
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(3)	(270)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	22,386	132,464
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (34)	$ (2,118)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	5	20
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 25,736	$ 157,345
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	(37)	(2,388)
CLO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	18,380	83,305
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(320)	(1,695)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	24,875	14,873
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (124)	$ (269)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	2	5
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 43,255	$ 98,178
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(444)	(1,964)
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	7,686	35,990
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(862)	(1,820)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	23,091	14,589
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (3,912)	$ (3,461)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | holding	7	8
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 30,777	$ 50,579
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(4,774)	(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		68,351
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(882)
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Fair Value	64,069	414,776
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (651)	$ (17,403)
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	25	223
Debt Securities, Held-to-maturity, Unrealized Loss Position, Fair Value	$ 64,069	$ 483,127
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss	$ (651)	$ (18,285)