Investment Securities (Summary Of Debt Securities Available-for-Sale) (Detail) $ in Thousands	Jun. 30, 2020 USD ($) numberOfHoldings	Dec. 31, 2019 USD ($) numberOfHoldings
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	$ 3,096,458	$ 2,901,415
Unrealized Gains	109,963	38,270
Unrealized Losses	(22,797)	(13,852)
Investment securities available-for-sale, at fair value	3,183,624	2,925,833
Interest receivable	55,500	59,000
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	535,098	607,521
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(18,759)	(1,914)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	55,237	762,631
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (4,038)	$ (11,938)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	77	157
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 590,335	$ 1,370,152
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(22,797)	(13,852)
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	1,705
Available-for-sale, Amortized Cost - Due after five through ten years	264,913
Available-for-sale, Amortized Cost - Due after ten years	2,829,840
Available-for-sale, Amortized Cost - Total debt securities	3,096,458	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	1,710
Available-for-sale, Fair Value - Due after five through ten years	255,748
Available-for-sale, Fair Value - Due after ten years	2,926,166
Debt Securities, Available-for-sale	3,183,624	2,925,833
Available-for-sale Securities [Member]
Debt Securities, Available-for-sale [Abstract]
Interest receivable	7,700	8,100
Agency CMO [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	182,484	184,500
Unrealized Gains	7,339	2,218
Unrealized Losses	(220)	(917)
Investment securities available-for-sale, at fair value	189,603	185,801
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	13,657	36,447
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(118)	(352)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	9,339	32,288
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (102)	$ (565)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	3	9
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 22,996	$ 68,735
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(220)	(917)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	182,484	184,500
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	189,603	185,801
Agency MBS [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	1,512,525	1,580,743
Unrealized Gains	75,054	35,456
Unrealized Losses	(343)	(4,035)
Investment securities available-for-sale, at fair value	1,587,236	1,612,164
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	28,377	41,408
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(149)	(193)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	13,154	299,674
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (194)	$ (3,842)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	27	79
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 41,531	$ 341,082
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(343)	(4,035)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	1,512,525	1,580,743
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	1,587,236	1,612,164
Agency CMBS [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	827,782	587,974
Unrealized Gains	27,131	513
Unrealized Losses	0	(6,935)
Investment securities available-for-sale, at fair value	854,913	581,552
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months		174,406
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		(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		34
Debt Securities, Available-for-sale, Unrealized Loss Position		$ 532,123
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss		(6,935)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	827,782	587,974
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	854,913	581,552
Non-agency CMBS [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	472,418	432,085
Unrealized Gains	433	38
Unrealized Losses	(16,597)	(252)
Investment securities available-for-sale, at fair value	456,254	431,871
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	424,793	355,260
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(16,204)	(232)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	7,107	7,480
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (393)	$ (20)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	40	29
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 431,900	$ 362,740
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(16,597)	(252)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	472,418	432,085
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	456,254	431,871
CLO [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	86,705	92,628
Unrealized Gains	6	45
Unrealized Losses	(2,228)	(468)
Investment securities available-for-sale, at fair value	84,483	92,205
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	64,791
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(1,509)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	17,982	43,232
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (719)	$ (468)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	4	2
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 82,773	$ 43,232
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(2,228)	(468)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	86,705	92,628
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	84,483	92,205
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Abstract]
Amortized Cost(1)	14,544	23,485
Unrealized Gains	0	0
Unrealized Losses	(3,409)	(1,245)
Investment securities available-for-sale, at fair value	11,135	22,240
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	3,480
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(779)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	7,655	22,240
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ (2,630)	$ (1,245)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | numberOfHoldings	3	4
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 11,135	$ 22,240
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	(3,409)	(1,245)
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Available-for-sale, Amortized Cost - Total debt securities	14,544	23,485
Debt Securities, Available-for-sale, Fair Value, Fiscal Year Maturity [Abstract]
Debt Securities, Available-for-sale	$ 11,135	$ 22,240