Loans Receivable - Schedule of Aging of Non-Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Non-Covered Loans Excluding Acquired Loans [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	$ 5,160	$ 10,345
Past Due, 60-89 days	3,348	2,447
Past Due, Greater than 90 days	48,515	49,288
Total past due	57,023	62,080
Current	6,933,960	6,685,425
Total non-covered loans, net of unearned income	6,990,983	6,747,505
Recorded investment > 90 days and accruing	1,950	1,371
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Mortgage Loans [Member] | Mortgage - Prime [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	876	662
Past Due, 60-89 days	1,570	1,156
Past Due, Greater than 90 days	9,425	9,168
Total past due	11,871	10,986
Current	176,807	185,843
Total non-covered loans, net of unearned income	188,678	196,829
Recorded investment > 90 days and accruing	1,266	801
Non-Covered Loans Excluding Acquired Loans [Member] | Residential Mortgage Loans [Member] | Mortgage - Subprime [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days
Past Due, 60-89 days	7
Past Due, Greater than 90 days
Total past due	7
Current	88,799	60,454
Total non-covered loans, net of unearned income	88,806	60,454
Recorded investment > 90 days and accruing
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate Construction [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	224	60
Past Due, 60-89 days
Past Due, Greater than 90 days	5,939	5,479
Total past due	6,163	5,539
Current	322,703	288,137
Total non-covered loans, net of unearned income	328,866	293,676
Recorded investment > 90 days and accruing
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate - Other [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	1,141	3,590
Past Due, 60-89 days	266
Past Due, Greater than 90 days	22,514	23,559
Total past due	23,921	27,149
Current	2,247,219	2,224,495
Total non-covered loans, net of unearned income	2,271,140	2,251,644
Recorded investment > 90 days and accruing	519	83
Non-Covered Loans Excluding Acquired Loans [Member] | Commercial Loans [Member] | Commercial Business [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	550	1,430
Past Due, 60-89 days	386	13
Past Due, Greater than 90 days	1,937	3,687
Total past due	2,873	5,130
Current	2,464,508	2,362,304
Total non-covered loans, net of unearned income	2,467,381	2,367,434
Recorded investment > 90 days and accruing	7	329
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer And Other Loans [Member] | Indirect Automobile [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	1,068	1,624
Past Due, 60-89 days	186	326
Past Due, Greater than 90 days	982	868
Total past due	2,236	2,818
Current	335,953	320,148
Total non-covered loans, net of unearned income	338,189	322,966
Recorded investment > 90 days and accruing
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer And Other Loans [Member] | Home Equity [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	882	2,283
Past Due, 60-89 days	705	796
Past Due, Greater than 90 days	6,966	5,793
Total past due	8,553	8,872
Current	1,016,663	991,766
Total non-covered loans, net of unearned income	1,025,216	1,000,638
Recorded investment > 90 days and accruing	158	158
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer And Other Loans [Member] | Credit Card [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	158	130
Past Due, 60-89 days	93	51
Past Due, Greater than 90 days	403	424
Total past due	654	605
Current	50,169	51,117
Total non-covered loans, net of unearned income	50,823	51,722
Recorded investment > 90 days and accruing
Non-Covered Loans Excluding Acquired Loans [Member] | Consumer And Other Loans [Member] | Other [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	261	566
Past Due, 60-89 days	135	105
Past Due, Greater than 90 days	349	310
Total past due	745	981
Current	231,139	201,161
Total non-covered loans, net of unearned income	231,884	202,142
Recorded investment > 90 days and accruing
Non-Covered Acquired Loans [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	7,893	10,502
Past Due, 60-89 days	3,519	2,499
Past Due, Greater than 90 days	50,925	52,781
Total past due	62,337	65,782
Current	617,544	675,692
Discount	(80,062)	(83,155)
Total non-covered loans, net of unearned income	599,819	658,319
Recorded investment > 90 days and accruing	50,925	52,781
Non-Covered Acquired Loans [Member] | Residential Mortgage Loans [Member] | Mortgage - Prime [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days
Past Due, 60-89 days
Past Due, Greater than 90 days	779	779
Total past due	779	779
Current	24,228	30,663
Discount	(1,202)	1,315
Total non-covered loans, net of unearned income	23,805	32,757
Recorded investment > 90 days and accruing	779	779
Non-Covered Acquired Loans [Member] | Residential Mortgage Loans [Member] | Mortgage - Subprime [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days
Past Due, 60-89 days
Past Due, Greater than 90 days
Total past due
Current
Discount
Total non-covered loans, net of unearned income
Recorded investment > 90 days and accruing
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate Construction [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	570	369
Past Due, 60-89 days	447
Past Due, Greater than 90 days	3,920	4,067
Total past due	4,937	4,436
Current	27,091	29,098
Discount	(4,154)	(3,968)
Total non-covered loans, net of unearned income	27,874	29,566
Recorded investment > 90 days and accruing	3,920	4,067
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Real Estate - Other [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	5,301	5,971
Past Due, 60-89 days	2,145	1,572
Past Due, Greater than 90 days	37,389	38,987
Total past due	44,835	46,530
Current	405,796	426,339
Discount	(58,440)	(57,055)
Total non-covered loans, net of unearned income	392,191	415,814
Recorded investment > 90 days and accruing	37,389	38,987
Non-Covered Acquired Loans [Member] | Commercial Loans [Member] | Commercial Business [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	845	1,410
Past Due, 60-89 days	112	524
Past Due, Greater than 90 days	2,684	3,953
Total past due	3,641	5,887
Current	70,777	89,490
Discount	(7,187)	(12,144)
Total non-covered loans, net of unearned income	67,231	83,233
Recorded investment > 90 days and accruing	2,684	3,953
Non-Covered Acquired Loans [Member] | Consumer And Other Loans [Member] | Indirect Automobile [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	67	171
Past Due, 60-89 days	22	4
Past Due, Greater than 90 days	123	146
Total past due	212	321
Current	3,716	4,698
Discount
Total non-covered loans, net of unearned income	3,928	5,019
Recorded investment > 90 days and accruing	123	146
Non-Covered Acquired Loans [Member] | Consumer And Other Loans [Member] | Home Equity [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	916	2,379
Past Due, 60-89 days	269	382
Past Due, Greater than 90 days	5,510	4,354
Total past due	6,695	7,115
Current	68,305	73,658
Discount	(7,523)	(4,498)
Total non-covered loans, net of unearned income	67,477	76,275
Recorded investment > 90 days and accruing	5,510	4,354
Non-Covered Acquired Loans [Member] | Consumer And Other Loans [Member] | Credit Card [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days
Past Due, 60-89 days
Past Due, Greater than 90 days
Total past due
Current
Discount
Total non-covered loans, net of unearned income
Recorded investment > 90 days and accruing
Non-Covered Acquired Loans [Member] | Consumer And Other Loans [Member] | Other [Member]
Loans Receivable [Line Items]
Past Due, 30-59 days	194	202
Past Due, 60-89 days	524	17
Past Due, Greater than 90 days	520	495
Total past due	1,238	714
Current	17,631	21,746
Discount	(1,556)	(6,805)
Total non-covered loans, net of unearned income	17,313	15,655
Recorded investment > 90 days and accruing	$ 520	$ 495