Investment Securities (Summary Of Debt Securities Available-for-Sale) (Detail) $ in Thousands	Mar. 31, 2020 USD ($) numberOfHoldings	Dec. 31, 2019 USD ($) numberOfHoldings
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 647,778	$ 607,521
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(50,053)	(1,914)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	101,277	762,631
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (7,318)	$ (11,938)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	101	157
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 749,055	$ 1,370,152
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(57,371)	(13,852)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	3,013,511	2,901,415
Unrealized Gains	60,491	38,270
Unrealized Losses	(57,371)	(13,852)
Investment securities available-for-sale, at fair value	3,016,631	2,925,833
Interest Receivable	61,500	59,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, within One Year, Amortized Cost	0
Available-for-sale, Amortized Cost - Due after one year through five years	0
Available-for-sale, Amortized Cost - Due after five through ten years	270,170
Available-for-sale, Amortized Cost - Due after ten years	2,743,341
Available-for-sale, Amortized Cost - Total debt securities	3,013,511	2,901,415
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale, Fair Value - Due in one year or less	0
Available-for-sale, Fair Value - Due after one year through five years	0
Available-for-sale, Fair Value - Due after five through ten years	244,659
Available-for-sale, Fair Value - Due after ten years	2,771,972
Debt Securities, Available-for-sale	3,016,631	2,925,833
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Abstract]
Interest Receivable	7,700	8,100
Agency CMO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		36,447
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(352)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	10,682	32,288
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (28)	$ (565)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	1	9
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 10,682	$ 68,735
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(28)	(917)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	197,019	184,500
Unrealized Gains	7,839	2,218
Unrealized Losses	(28)	(917)
Investment securities available-for-sale, at fair value	204,830	185,801
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	197,019	184,500
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	204,830	185,801
Agency MBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	34,313	41,408
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(180)	(193)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	60,837	299,674
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (566)	$ (3,842)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	38	79
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 95,150	$ 341,082
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(746)	(4,035)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	1,565,689	1,580,743
Unrealized Gains	47,875	35,456
Unrealized Losses	(746)	(4,035)
Investment securities available-for-sale, at fair value	1,612,818	1,612,164
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	1,565,689	1,580,743
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	1,612,818	1,612,164
Agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	145,948	174,406
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	$ (454)	(1,137)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer		357,717
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		$ (5,798)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	10	34
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 145,948	$ 532,123
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(454)	(6,935)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	693,371	587,974
Unrealized Gains	4,765	513
Unrealized Losses	(454)	(6,935)
Investment securities available-for-sale, at fair value	697,682	581,552
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	693,371	587,974
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	697,682	581,552
Non-agency CMBS [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	402,409	355,260
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(43,971)	(232)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	6,615	7,480
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (885)	$ (20)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	45	29
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 409,024	$ 362,740
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(44,856)	(252)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	453,879	432,085
Unrealized Gains	0	38
Unrealized Losses	(44,856)	(252)
Investment securities available-for-sale, at fair value	409,023	431,871
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	453,879	432,085
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	409,023	431,871
CLO [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	61,708
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(4,592)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	15,663	43,232
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (3,037)	$ (468)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	4	2
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 77,371	$ 43,232
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(7,629)	(468)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	89,015	92,628
Unrealized Gains	12	45
Unrealized Losses	(7,629)	(468)
Investment securities available-for-sale, at fair value	81,398	92,205
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	89,015	92,628
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	81,398	92,205
Corporate Debt Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,400
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(856)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	7,480	22,240
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (2,802)	$ (1,245)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	3	4
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 10,880	$ 22,240
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(3,658)	(1,245)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	14,538	23,485
Unrealized Gains	0	0
Unrealized Losses	(3,658)	(1,245)
Investment securities available-for-sale, at fair value	10,880	22,240
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	14,538	23,485
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	$ 10,880	$ 22,240