Investment Securities (Gross Unrealized Losses and Fair Values by Investment and Length of Time Of Securities) (Detail) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 283,336,000	$ 1,192,634,000
Unrealized Losses, Less than 12 Months	1,810,000	24,730,000
Fair Value, 12 Months or More	413,878,000	26,417,000
Unrealized Losses, 12 Months or More	24,045,000	15,360,000
Fair Value, Total	697,214,000	1,219,051,000
Unrealized Losses, Total	25,855,000	40,090,000
U.S. Government Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	24,953,000	68,111,000
Unrealized Losses, Less than 12 Months	47,000	422,000
Fair Value, 12 Months or More	1,947,000	0
Unrealized Losses, 12 Months or More	53,000	0
Fair Value, Total	26,900,000	68,111,000
Unrealized Losses, Total	100,000	422,000
Obligations Of States And Political Subdivisions [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	73,895,000
Unrealized Losses, Less than 12 Months	0	3,910,000
Fair Value, 12 Months or More	59,429,000	7,025,000
Unrealized Losses, 12 Months or More	1,275,000	165,000
Fair Value, Total	59,429,000	80,920,000
Unrealized Losses, Total	1,275,000	4,075,000
Agency Residential Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	258,383,000	1,030,987,000
Unrealized Losses, Less than 12 Months	1,763,000	20,104,000
Fair Value, 12 Months or More	331,792,000	0
Unrealized Losses, 12 Months or More	8,804,000	0
Fair Value, Total	590,175,000	1,030,987,000
Unrealized Losses, Total	10,567,000	20,104,000
Non-Agency Residential Mortgage-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	530,000
Unrealized Losses, Less than 12 Months	0	8,000
Fair Value, 12 Months or More	352,000	0
Unrealized Losses, 12 Months or More	5,000	0
Fair Value, Total	352,000	530,000
Unrealized Losses, Total	5,000	8,000
Other Structured Financial Products [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or More	11,995,000	11,297,000
Unrealized Losses, 12 Months or More	12,746,000	13,741,000
Fair Value, Total	11,995,000	11,297,000
Unrealized Losses, Total	12,746,000	13,741,000
Other Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	0
Unrealized Losses, Less than 12 Months	0	0
Fair Value, 12 Months or More	6,786,000	6,476,000
Unrealized Losses, 12 Months or More	273,000	557,000
Fair Value, Total	6,786,000	6,476,000
Unrealized Losses, Total	273,000	557,000
Other Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	0	19,111,000
Unrealized Losses, Less than 12 Months	0	286,000
Fair Value, 12 Months or More	1,577,000	1,619,000
Unrealized Losses, 12 Months or More	889,000	897,000
Fair Value, Total	1,577,000	20,730,000
Unrealized Losses, Total	$ 889,000	$ 1,183,000