Investment Securities (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 holding		Dec. 31, 2012 holding		Dec. 31, 2011
Schedule of Investments [Line Items]
Pledged securities as required or permitted by law	$ 2,700,000,000		$ 2,500,000,000
Marketable Securities	6,469,633,000		6,176,711,000
Percent of government obligations to consolidated shareholders' equity maximum	10.00%		10.00%
Available-for-sale - Gross unrealized losses, Recognized in OCI	61,626,000		31,489,000
Securities available for sale, at fair value	3,106,931,000		3,136,160,000
Held-to-maturity Securities, Unrecognized holding loss	61,218,000		592,000
Number of Positions	164		24
Other-than-temporary impairments	7,277,000		0		0
Callable [Member]
Schedule of Investments [Line Items]
Carrying value	849,300,000
US States and Political Subdivisions Debt Securities [Member]
Schedule of Investments [Line Items]
Marketable Securities	0		0
Agency collateralized mortgage obligations (CMOs) [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	1,868,000		92,000
Securities available for sale, at fair value	806,912,000		1,310,006,000
Held-to-maturity Securities, Unrecognized holding loss	1,009,000		8,000
Number of Positions	4		1
Agency mortage-backed securities (MBS) [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	47,698,000		1,098,000
Securities available for sale, at fair value	1,226,702,000		1,142,280,000
Held-to-maturity Securities, Unrecognized holding loss	53,188,000		474,000
Number of Positions	94		12
Agency CMBS [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	782,000
Securities available for sale, at fair value	70,977,000
Held-to-maturity Securities, Unrecognized holding loss	818,000
Number of Positions	4
Commercial mortgage-backed securities (CMBS) [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	996,000		3,493,000
Securities available for sale, at fair value	464,274,000		398,031,000
Held-to-maturity Securities, Unrecognized holding loss	4,975,000		0
Number of Positions	11
Collateralized Loan Obligations [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	2,600,000	[1]	225,000
Securities available for sale, at fair value	357,641,000	[1]	88,540,000
Pooled trust preferred securities [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	3,410,000	[2]	19,811,000	[3]
Securities available for sale, at fair value	28,490,000	[2]	26,207,000	[3]
Increase in pooled issuers trust preferred securities	2,300,000
Decrease in available-for-sale securities, gross unrealized loss	16,400,000
Single issuer trust preferred securities [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	6,872,000		6,766,000
Number of securities	1
Securities available for sale, at fair value	34,935,000		44,415,000
Decrease in available-for-sale securities, gross unrealized loss	(100,000)
Increase in trust preferred securities - single issuers	(9,500,000)
Equity securities - financial institutions [Member]
Schedule of Investments [Line Items]
Available-for-sale - Gross unrealized losses, Recognized in OCI	0	[4]	4,000	[5]
Securities available for sale, at fair value	3,584,000	[4]	8,282,000	[5]
Municipal Bonds [Member]
Schedule of Investments [Line Items]
Held-to-maturity Securities, Unrecognized holding loss	1,228,000		110,000
Percentage of bank qualified bonds with credit rating range of AAA to A	95.60%
Percentage of municipal bond Portfolio comprised of General Obligation bonds	85.10%
Percentage of municipal bond portfolio comprised of Revenue bonds	14.40%
Percentage of municipal bond portfolio comprised of other bonds	0.50%
Number of Positions	51		11
Pooled trust preferred securities [Member]
Schedule of Investments [Line Items]
Carrying value	28,490,000
Available-for-sale - Gross unrealized losses, Recognized in OCI	3,410,000
Other-than-temporary impairments	$ 4,666,000

[1] Amortized cost is net of $2.6 million of other-than-temporary impairment at December 31, 2013.

[2] Amortized cost is net of $14.0 million of other-than-temporary impairment at December 31, 2013

[3] Amortized cost is net of $10.5 million of credit related other-than-temporary impairment at December 31, 2012.

[4] Amortized cost is net of $20.4 million of other-than-temporary impairment at December 31, 2013.

[5] Amortized cost is net of $21.3 million of other-than-temporary impairment at December 31, 2012.