Investment Securities (Summary Of Investment Securities) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Amortized Cost	$ 2,994,924	$ 2,767,967
Unrealized Gains	22,997	44,649
Unrealized Losses	(33,290)	(18,743)
Fair Value	2,984,631	2,793,873
Held-to-maturity Securities [Abstract]
Amortized Cost	3,923,052	3,872,955
Unrealized Gains	63,894	90,043
Unrealized Losses	(25,412)	(14,292)
Fair Value	3,961,534	3,948,706
US Treasury Bill Securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	924	525
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	924	525
Agency collateralized mortgage obligations (agency CMO) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	546,168	543,417
Unrealized Gains	5,532	8,636
Unrealized Losses	(2,946)	(1,065)
Fair Value	548,754	550,988
Held-to-maturity Securities [Abstract]
Amortized Cost	407,494	442,129
Unrealized Gains	3,717	6,584
Unrealized Losses	(2,058)	(739)
Fair Value	409,153	447,974
Agency mortgage-backed securities (agency MBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	1,075,941	1,030,724
Unrealized Gains	6,459	10,462
Unrealized Losses	(17,291)	(12,668)
Fair Value	1,065,109	1,028,518
Held-to-maturity Securities [Abstract]
Amortized Cost	2,030,176	2,134,319
Unrealized Gains	38,813	57,196
Unrealized Losses	(19,908)	(11,340)
Fair Value	2,049,081	2,180,175
Agency commercial mortgage-backed securities (agency CMBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	215,670	80,400
Unrealized Gains	639	0
Unrealized Losses	(959)	(134)
Fair Value	215,350	80,266
Held-to-maturity Securities [Abstract]
Amortized Cost	686,086	578,687
Unrealized Gains	4,253	1,597
Unrealized Losses	(325)	(1,143)
Fair Value	690,014	579,141
Non-agency commercial mortgage-backed securities (non-agency CMBS) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	574,686	534,631
Unrealized Gains	7,485	18,885
Unrealized Losses	(2,905)	(123)
Fair Value	579,266	553,393
Held-to-maturity Securities [Abstract]
Amortized Cost	360,018	338,723
Unrealized Gains	5,046	9,428
Unrealized Losses	(2,704)	(1,015)
Fair Value	362,360	347,136
Collateralized loan obligations (CLO) [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	431,837	426,269
Unrealized Gains	592	482
Unrealized Losses	(3,270)	(1,017)
Fair Value	429,159	425,734
Single issuer trust preferred securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	42,168	41,981
Unrealized Gains	0	0
Unrealized Losses	(4,998)	(3,736)
Fair Value	37,170	38,245
Corporate debt securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	104,031	106,520
Unrealized Gains	2,290	3,781
Unrealized Losses	0	0
Fair Value	106,321	110,301
Equity securities [Member]
Available-for-sale Securities [Abstract]
Amortized Cost	3,499	3,500
Unrealized Gains	0	2,403
Unrealized Losses	(921)	0
Fair Value	2,578	5,903
Municipal bonds and notes [Member]
Held-to-maturity Securities [Abstract]
Amortized Cost	435,905	373,211
Unrealized Gains	12,019	15,138
Unrealized Losses	(417)	(55)
Fair Value	447,507	388,294
Private Label MBS [Member]
Held-to-maturity Securities [Abstract]
Amortized Cost	3,373	5,886
Unrealized Gains	46	100
Unrealized Losses	0	0
Fair Value	$ 3,419	$ 5,986

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

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