Available-For-Sale Securities (Summary Of The Available-For-Sale Securities Portfolio) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,867,574		$ 1,785,113		$ 1,866,314
Gross unrealized gains	17,544		20,556		21,334
Gross unrealized losses	(14,287)		(9,593)		(18,304)
Fair Value	1,870,831		1,796,076		1,869,344
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	220,215		220,226		23,063
Gross unrealized gains	190		198		128
Gross unrealized losses	(2,760)		(937)		(2)
Fair Value	217,645		219,487		23,189
U.S. Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	975,386		986,186		682,847
Gross unrealized gains	2,960		4,839		4,082
Gross unrealized losses	(4,631)		(986)		(4,149)
Fair Value	973,715		990,039		682,780
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	107,947		107,868		67,970
Gross unrealized gains	2,628		2,899		1,963
Gross unrealized losses	(316)		(296)		(18)
Fair Value	110,259		110,471		69,915
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	136,761		142,205		148,492
Gross unrealized gains	2,569		2,452		2,569
Gross unrealized losses	(2,280)		(3,982)		(9,044)
Fair Value	137,050		140,675		142,017
Corporate Notes And Other, Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,628		13,911		26,475
Gross unrealized gains	195		220		329
Gross unrealized losses	0		0		(5)
Fair Value	11,823		14,131		26,799
Mortgage Backed Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	294,728	[1]	188,485	[1]	846,380	[1]
Gross unrealized gains	7,360	[1]	8,805	[1]	11,866	[1]
Gross unrealized losses	(3,194)	[1]	(30)	[1]	(806)	[1]
Fair Value	298,894	[1]	197,260	[1]	857,440	[1]
Mortgage-Backed, Non-Agency CMOs [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	68,496	[1]	73,386	[1]	28,423	[1]
Gross unrealized gains	897	[1]	928	[1]	286	[1]
Gross unrealized losses	(5)	[1]	0	[1]	(1)	[1]
Fair Value	69,388	[1]	74,314	[1]	28,708	[1]
Other equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	52,413		52,846		42,664
Gross unrealized gains	745		215		111
Gross unrealized losses	(1,101)		(3,362)		(4,279)
Fair Value	$ 52,057		$ 49,699		$ 38,496

[1] Consisting entirely of residential mortgage-backed securities, none of which are subprime.