Investment Securities (Summary Of Gross Unrealized Losses Not Considered OTTI) (Detail) $ in Thousands	Jun. 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	$ 1,250,149	$ 1,236,547
Available for sale, Unrealized Losses - Less Than Twelve Months	(25,807)	(27,316)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	358,432	470,314
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (10,171)	$ (13,582)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	165	168
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 1,608,581	$ 1,706,861
Available for sale, Unrealized Losses - Total	(35,978)	(40,898)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	2,261,483	2,351,350
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(44,991)	(63,785)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	335,335	292,225
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (10,878)	$ (9,315)
Held-to-maturity, Number of Holdings - Total | holding	358	395
Held-to-maturity, Fair Value - Total	$ 2,596,818	$ 2,643,575
Held-to-maturity, Unrealized Losses - Total	(55,869)	(73,100)
Agency CMO [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	90,691	107,853
Available for sale, Unrealized Losses - Less Than Twelve Months	(1,941)	(2,168)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	60,635	67,351
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (1,182)	$ (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	$ 151,326	$ 175,204
Available for sale, Unrealized Losses - Total	(3,123)	(3,503)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	98,593	163,439
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(2,288)	(3,339)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	51,844	17,254
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (882)	$ (485)
Held-to-maturity, Number of Holdings - Total | holding	15	16
Held-to-maturity, Fair Value - Total	$ 150,437	$ 180,693
Held-to-maturity, Unrealized Losses - Total	(3,170)	(3,824)
Agency MBS [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	463,242	512,075
Available for sale, Unrealized Losses - Less Than Twelve Months	(8,396)	(10,503)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	250,375	252,779
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (8,488)	$ (9,006)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	101	97
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 713,617	$ 764,854
Available for sale, Unrealized Losses - Total	(16,884)	(19,509)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	1,315,939	1,394,623
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(27,429)	(32,942)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	252,535	273,779
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (7,686)	$ (8,826)
Held-to-maturity, Number of Holdings - Total | holding	149	150
Held-to-maturity, Fair Value - Total	$ 1,568,474	$ 1,668,402
Held-to-maturity, Unrealized Losses - Total	(35,115)	(41,768)
Agency CMBS [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	582,194	554,246
Available for sale, Unrealized Losses - Less Than Twelve Months	(15,154)	$ (14,567)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,908
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (190)
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	$ 587,102	$ 554,246
Available for sale, Unrealized Losses - Total	(15,344)	(14,567)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	493,652	347,725
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	$ (2,727)	$ (1,348)
Held-to-maturity, Number of Holdings - Total | holding	39	25
Held-to-maturity, Fair Value - Total	$ 493,652	$ 347,725
Held-to-maturity, Unrealized Losses - Total	(2,727)	(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	43,970	12,427
Available for sale, Unrealized Losses - Less Than Twelve Months	(30)	(24)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	19,804	63,930
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (196)	$ (678)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	6	12
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 63,774	$ 76,357
Available for sale, Unrealized Losses - Total	(226)	(702)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	38,756	60,768
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	$ (252)	$ (411)
Held-to-maturity, Number of Holdings - Total | holding	7	8
Held-to-maturity, Fair Value - Total	$ 38,756	$ 60,768
Held-to-maturity, Unrealized Losses - Total	(252)	(411)
CLO [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	58,674	49,946
Available for sale, Unrealized Losses - Less Than Twelve Months	(203)	(54)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	16,263	50,237
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (21)	$ (465)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	4	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 74,937	$ 100,183
Available for sale, Unrealized Losses - Total	(224)	(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	5,527	0
Available for sale, Unrealized Losses - Less Than Twelve Months	(53)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	4,606	28,633
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (70)	$ (1,748)
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | holding	2	5
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 10,133	$ 28,633
Available for sale, Unrealized Losses - Total	(123)	(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	5,851
Available for sale, Unrealized Losses - Less Than Twelve Months	(30)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	1,841	7,384
Available for sale, Unrealized Losses - Twelve Months or Longer	$ (24)	$ (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	$ 7,692	$ 7,384
Available for sale, Unrealized Losses - Total	(54)	(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	314,543	384,795
Held-to-maturity, Unrealized Losses - Less Than Twelve Months	(12,295)	(25,745)
Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value	30,956	1,192
Held-to-maturity, Unrealized Losses, Twelve Months or Longer	$ (2,310)	$ (4)
Held-to-maturity, Number of Holdings - Total | holding	148	196
Held-to-maturity, Fair Value - Total	$ 345,499	$ 385,987
Held-to-maturity, Unrealized Losses - Total	$ (14,605)	$ (25,749)