Available-For-Sale Securities (Schedule Of Available-For-Sale Securities Reconciliation) (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Mar. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 2,015,966		$ 2,265,118		$ 1,867,574
Gross unrealized gains	17,212		11,758		17,544
Gross unrealized losses	(83,481)		(100,586)		(14,287)
Available-for-sale securities, at fair value	1,949,697		2,176,290		1,870,831
US Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	354,109		354,262		220,215
Gross unrealized gains	263		141		190
Gross unrealized losses	(14,194)		(18,308)		(2,760)
Available-for-sale securities, at fair value	340,178		336,095		217,645
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	874,845		950,086		975,386
Gross unrealized gains	3,286		1,680		2,960
Gross unrealized losses	(49,856)		(56,078)		(4,631)
Available-for-sale securities, at fair value	828,275		895,688		973,715
Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	175,028		154,463		107,947
Gross unrealized gains	3,439		2,551		2,628
Gross unrealized losses	(3,167)		(4,298)		(316)
Available-for-sale securities, at fair value	175,300		152,716		110,259
Corporate Notes, Financial Issuers [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	129,413		129,362		136,761
Gross unrealized gains	2,306		1,993		2,569
Gross unrealized losses	(1,735)		(2,411)		(2,280)
Available-for-sale securities, at fair value	129,984		128,944		137,050
Corporate Notes, Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	4,986		5,994		11,628
Gross unrealized gains	100		105		195
Gross unrealized losses	(3)		(5)		0
Available-for-sale securities, at fair value	5,083		6,094		11,823
Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	371,825	[1]	562,708	[1]	294,728	[1]
Gross unrealized gains	3,919	[1]	3,537	[1]	7,360	[1]
Gross unrealized losses	(13,188)	[1]	(18,047)	[1]	(3,194)	[1]
Available-for-sale securities, at fair value	362,556	[1]	548,198	[1]	298,894	[1]
Mortgage-Backed, Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	55,190	[1]	57,711	[1]	68,496	[1]
Gross unrealized gains	356	[1]	258	[1]	897	[1]
Gross unrealized losses	(799)	[1]	(942)	[1]	(5)	[1]
Available-for-sale securities, at fair value	54,747	[1]	57,027	[1]	69,388	[1]
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	50,570		50,532		52,413
Gross unrealized gains	3,543		1,493		745
Gross unrealized losses	(539)		(497)		(1,101)
Available-for-sale securities, at fair value	$ 53,574		$ 51,528		$ 52,057

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