Investment Securities (Summary Of Investment Securities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities [Abstract]
Amortized Cost	$ 3,015,763	$ 2,994,924
Unrealized Gains	16,226	22,997
Unrealized Losses	(40,898)	(33,290)
Fair Value	2,991,091	2,984,631
Held-to-maturity Securities [Abstract]
Amortized Cost	4,160,658	3,923,052
Unrealized Gains	37,567	63,894
Unrealized Losses	(73,100)	(25,412)
Fair Value	4,125,125	3,961,534
US Treasury Bill Securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	734	924
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	734	924
Agency collateralized mortgage obligations (agency CMO) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	419,865	546,168
Unrealized Gains	3,344	5,532
Unrealized Losses	(3,503)	(2,946)
Fair Value	419,706	548,754
Held-to-maturity Securities [Abstract]
Amortized Cost	339,455	407,494
Unrealized Gains	1,977	3,717
Unrealized Losses	(3,824)	(2,058)
Fair Value	337,608	409,153
Agency mortgage-backed securities (agency MBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	969,460	1,075,941
Unrealized Gains	4,398	6,459
Unrealized Losses	(19,509)	(17,291)
Fair Value	954,349	1,065,109
Held-to-maturity Securities [Abstract]
Amortized Cost	2,317,449	2,030,176
Unrealized Gains	26,388	38,813
Unrealized Losses	(41,768)	(19,908)
Fair Value	2,302,069	2,049,081
Agency commercial mortgage-backed securities (agency CMBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	587,776	215,670
Unrealized Gains	63	639
Unrealized Losses	(14,567)	(959)
Fair Value	573,272	215,350
Held-to-maturity Securities [Abstract]
Amortized Cost	547,726	686,086
Unrealized Gains	694	4,253
Unrealized Losses	(1,348)	(325)
Fair Value	547,072	690,014
Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	473,974	574,686
Unrealized Gains	4,093	7,485
Unrealized Losses	(702)	(2,905)
Fair Value	477,365	579,266
Held-to-maturity Securities [Abstract]
Amortized Cost	298,538	360,018
Unrealized Gains	4,107	5,046
Unrealized Losses	(411)	(2,704)
Fair Value	302,234	362,360
Collateralized loan obligations (CLO) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	425,083	431,837
Unrealized Gains	2,826	592
Unrealized Losses	(519)	(3,270)
Fair Value	427,390	429,159
Single issuer trust preferred securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	30,381	42,168
Unrealized Gains	0	0
Unrealized Losses	(1,748)	(4,998)
Fair Value	28,633	37,170
Corporate debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	108,490	104,031
Unrealized Gains	1,502	2,290
Unrealized Losses	(350)	0
Fair Value	109,642	106,321
Equity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	0	3,499
Unrealized Gains	0	0
Unrealized Losses	0	(921)
Fair Value	0	2,578
Municipal bonds and notes [Member]
Held-to-maturity Securities [Abstract]
Amortized Cost	655,813	435,905
Unrealized Gains	4,389	12,019
Unrealized Losses	(25,749)	(417)
Fair Value	634,453	447,507
Private Label MBS [Member]
Held-to-maturity Securities [Abstract]
Amortized Cost	1,677	3,373
Unrealized Gains	12	46
Unrealized Losses	0	0
Fair Value	$ 1,689	$ 3,419

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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