Allowance for Credit Losses and Credit Quality - Investment in Covered Loans and Non-Covered Loans by Credit Quality Indicator (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-covered commercial loans, net	$ 7,590,802	$ 7,405,824
Total loans receivable	1,004,173	1,092,756
Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	6,933,960	6,685,425
Credit risk by payment status, Past due greater than 30 days	57,023	62,080
Discount	6,990,983	6,747,505
Covered Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	268,559
Covered Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	75,587
Covered Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	363,058
Covered Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	9,291
Covered Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	716,495
Discount	(61,842)
Total loans receivable	654,653
Covered Loans [Member] | Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	177,811	183,795
Credit risk by payment status, Past due greater than 30 days	44,777	52,379
Credit quality indicator by asset risk classification	222,588	236,174
Discount	(45,260)	(49,010)
Covered Loans [Member] | Mortgage [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-covered commercial loans, net		187,164
Total loans receivable	177,328
Covered Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	167,997	170,724
Credit risk by payment status, Past due greater than 30 days	56,596	67,585
Credit quality indicator by asset risk classification	224,593	238,309
Discount	(52,401)	(60,611)
Covered Loans [Member] | Consumer Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans receivable	172,192	177,698
Covered Loans [Member] | Commercial Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		286,014
Covered Loans [Member] | Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		83,986
Covered Loans [Member] | Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		426,504
Covered Loans [Member] | Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		9,588
Covered Loans [Member] | Commercial Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		806,092
Discount		(78,198)
Total loans receivable		727,894
Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	24,619	25,896
Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	2,017	2,410
Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	5,392	5,228
Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification
Commercial Real Estate Construction [Member] | Non-Covered Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans receivable	32,028	33,534
Non-covered commercial loans, net	27,874	29,566
Discount	(4,154)	(3,968)
Commercial Real Estate Construction [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	307,334	269,842
Commercial Real Estate Construction [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	14,016	16,767
Commercial Real Estate Construction [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	7,516	7,067
Commercial Real Estate Construction [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification
Commercial Real Estate Construction [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-covered commercial loans, net	328,866	293,676
Discount
Non-covered commercial loans, net	328,866	293,676
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	48,695
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	9,568
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	79,496
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	607
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	138,366
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Commercial Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		46,201
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		9,888
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		97,315
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		607
Commercial Real Estate Construction [Member] | Covered Loans [Member] | Commercial Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		154,011
Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	341,260	359,046
Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	28,730	28,185
Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	76,232	85,420
Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	4,409	218
Commercial Real Estate - Other [Member] | Non-Covered Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans receivable	450,631	472,869
Non-covered commercial loans, net	392,191	415,814
Discount	(58,440)	(57,055)
Commercial Real Estate - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	2,197,301	2,162,989
Commercial Real Estate - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	33,328	40,547
Commercial Real Estate - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	40,113	47,710
Commercial Real Estate - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	398	398
Commercial Real Estate - Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-covered commercial loans, net	2,271,140	2,251,644
Discount
Non-covered commercial loans, net	2,271,140	2,251,644
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	185,652
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	62,980
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	241,459
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	8,241
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	498,332
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Commercial Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		201,261
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		65,498
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		279,171
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		8,530
Commercial Real Estate - Other [Member] | Covered Loans [Member] | Commercial Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		554,460
Commercial Business [Member] | Non-Covered Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	65,815	86,201
Commercial Business [Member] | Non-Covered Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	3,758	2,159
Commercial Business [Member] | Non-Covered Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	3,914	4,808
Commercial Business [Member] | Non-Covered Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	931	2,209
Commercial Business [Member] | Non-Covered Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans receivable	74,418	95,377
Non-covered commercial loans, net	67,231	83,233
Discount	(7,187)	(12,144)
Commercial Business [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	2,405,197	2,295,788
Commercial Business [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	19,896	21,640
Commercial Business [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	42,240	49,958
Commercial Business [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	48	48
Commercial Business [Member] | Non-Covered Loans Excluding Acquired Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Non-covered commercial loans, net	2,467,381	2,367,434
Discount
Non-covered commercial loans, net	2,467,381	2,367,434
Commercial Business [Member] | Covered Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	34,212
Commercial Business [Member] | Covered Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	3,039
Commercial Business [Member] | Covered Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	42,103
Commercial Business [Member] | Covered Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	443
Commercial Business [Member] | Covered Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification	79,797
Commercial Business [Member] | Covered Loans [Member] | Commercial Loans [Member] | Pass [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		38,552
Commercial Business [Member] | Covered Loans [Member] | Commercial Loans [Member] | Special Mention [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		8,600
Commercial Business [Member] | Covered Loans [Member] | Commercial Loans [Member] | Substandard [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		50,018
Commercial Business [Member] | Covered Loans [Member] | Commercial Loans [Member] | Doubtful [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		451
Commercial Business [Member] | Covered Loans [Member] | Commercial Loans [Member] | Internally Assigned Grade [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit quality indicator by asset risk classification		97,621
Mortgage - Prime [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	24,228	30,663
Credit risk by payment status, Past due greater than 30 days	779	779
Total loans receivable	25,007	31,442
Premium (discount)	(1,202)	1,315
Non-covered commercial loans, net	23,805	32,757
Mortgage - Prime [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	176,807	185,843
Credit risk by payment status, Past due greater than 30 days	11,871	10,986
Non-covered commercial loans, net	188,678	196,829
Discount
Non-covered commercial loans, net	188,678	196,829
Mortgage - Prime [Member] | Covered Loans [Member] | Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	177,811	183,795
Credit risk by payment status, Past due greater than 30 days	44,777	52,379
Credit quality indicator by asset risk classification	222,588	236,174
Mortgage - Subprime [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current
Credit risk by payment status, Past due greater than 30 days
Total loans receivable
Premium (discount)
Non-covered commercial loans, net
Mortgage - Subprime [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	88,799	60,454
Credit risk by payment status, Past due greater than 30 days	7
Non-covered commercial loans, net	88,806	60,454
Discount
Non-covered commercial loans, net	88,806	60,454
Mortgage - Subprime [Member] | Covered Loans [Member] | Mortgage [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current
Credit risk by payment status, Past due greater than 30 days
Credit quality indicator by asset risk classification
Indirect Automobile [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	3,716	4,698
Credit risk by payment status, Past due greater than 30 days	212	321
Total loans receivable	3,928	5,019
Premium (discount)
Non-covered commercial loans, net	3,928	5,019
Indirect Automobile [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	335,953	320,148
Credit risk by payment status, Past due greater than 30 days	2,236	2,818
Non-covered commercial loans, net	338,189	322,966
Indirect Automobile [Member] | Covered Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current
Credit risk by payment status, Past due greater than 30 days
Credit quality indicator by asset risk classification
Credit Card [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current
Credit risk by payment status, Past due greater than 30 days
Total loans receivable
Premium (discount)
Non-covered commercial loans, net
Credit Card [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	50,169	51,117
Credit risk by payment status, Past due greater than 30 days	654	605
Non-covered commercial loans, net	50,823	51,722
Credit Card [Member] | Covered Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	784	841
Credit risk by payment status, Past due greater than 30 days	35	65
Credit quality indicator by asset risk classification	819	906
Home Equity [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	68,305	73,658
Credit risk by payment status, Past due greater than 30 days	6,695	7,115
Total loans receivable	75,000	80,773
Discount	(7,523)	(4,498)
Non-covered commercial loans, net	67,477	76,275
Home Equity [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	1,016,663	991,766
Credit risk by payment status, Past due greater than 30 days	8,553	8,872
Non-covered commercial loans, net	1,025,216	1,000,638
Discount
Non-covered commercial loans, net	1,025,216	1,000,638
Home Equity [Member] | Covered Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	166,129	168,728
Credit risk by payment status, Past due greater than 30 days	54,924	65,997
Credit quality indicator by asset risk classification	221,053	234,725
Other [Member] | Non-Covered Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	17,631	21,746
Credit risk by payment status, Past due greater than 30 days	1,238	714
Total loans receivable	18,869	22,460
Discount	(1,556)	(6,805)
Non-covered commercial loans, net	17,313	15,655
Other [Member] | Non-Covered Loans Excluding Acquired Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	231,139	201,161
Credit risk by payment status, Past due greater than 30 days	745	981
Non-covered commercial loans, net	231,884	202,142
Discount
Non-covered commercial loans, net	231,884	202,142
Other [Member] | Covered Loans [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Credit risk by payment status, Current	1,084	1,155
Credit risk by payment status, Past due greater than 30 days	1,637	1,523
Credit quality indicator by asset risk classification	$ 2,721	$ 2,678