Loans - Summary of Age Analysis of Past Due Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	$ 85,960	$ 45,381
60-89 days past due	28,347	8,218
Greater than 90 days past due	85,726	109,150
Total past due	200,033	162,749
Current	11,377,769	11,014,277
Total Loans	11,577,802	11,177,026
Recorded investment > 90 days and accruing	13,243	5,880
Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	46,246	43,683
60-89 days past due	21,961	7,788
Greater than 90 days past due	54,686	88,178
Total past due	122,893	139,649
Current	6,984,328	4,748,081
Total Loans	7,107,221	4,887,730
Recorded investment > 90 days and accruing	7,736	4,871
Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	39,714	1,698
60-89 days past due	6,386	430
Greater than 90 days past due	26,940	2,126
Total past due	73,040	4,254
Current	3,881,718	5,613,599
Total Loans	3,954,758	5,617,853
Recorded investment > 90 days and accruing	5,507	1,009
Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Greater than 90 days past due	4,100	18,846
Total past due	4,100	18,846
Current	511,723	652,597
Total Loans	515,823	671,443
Commercial loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	53,189	23,996
60-89 days past due	21,174	943
Greater than 90 days past due	65,836	77,076
Total past due	140,199	102,015
Current	8,205,489	7,960,143
Total Loans	8,345,688	8,062,158
Recorded investment > 90 days and accruing	9,616	3,821
Commercial loans [Member] | Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	24,398	23,996
60-89 days past due	16,508	943
Greater than 90 days past due	46,355	58,867
Total past due	87,261	83,806
Current	4,840,199	3,242,166
Total Loans	4,927,460	3,325,972
Recorded investment > 90 days and accruing	5,262	3,821
Commercial loans [Member] | Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	28,791
60-89 days past due	4,666
Greater than 90 days past due	15,774
Total past due	49,231
Current	3,216,109	4,496,644
Total Loans	3,265,340	4,496,644
Recorded investment > 90 days and accruing	4,354
Commercial loans [Member] | Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Greater than 90 days past due	3,707	18,209
Total past due	3,707	18,209
Current	149,181	221,333
Total Loans	152,888	239,542
Residential mortgage loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	21,141	17,884
60-89 days past due	4,593	4,364
Greater than 90 days past due	13,489	26,037
Total past due	39,223	48,285
Current	1,538,721	1,459,213
Total Loans	1,577,944	1,507,498
Recorded investment > 90 days and accruing	1,106	994
Residential mortgage loans [Member] | Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	11,500	17,884
60-89 days past due	3,303	4,364
Greater than 90 days past due	4,100	25,400
Total past due	18,903	47,648
Current	809,082	439,499
Total Loans	827,985	487,147
Recorded investment > 90 days and accruing		994
Residential mortgage loans [Member] | Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	9,641
60-89 days past due	1,290
Greater than 90 days past due	8,996
Total past due	19,927
Current	466,517	734,669
Total Loans	486,444	734,669
Recorded investment > 90 days and accruing	1,106
Residential mortgage loans [Member] | Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Greater than 90 days past due	393	637
Total past due	393	637
Current	263,122	285,045
Total Loans	263,515	285,682
Consumer loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	11,630	3,501
60-89 days past due	2,580	2,911
Greater than 90 days past due	6,401	6,037
Total past due	20,611	12,449
Current	1,633,559	1,594,921
Total Loans	1,654,170	1,607,370
Recorded investment > 90 days and accruing	2,521	1,065
Consumer loans [Member] | Originated loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	10,348	1,803
60-89 days past due	2,150	2,481
Greater than 90 days past due	4,231	3,911
Total past due	16,729	8,195
Current	1,335,047	1,066,416
Total Loans	1,351,776	1,074,611
Recorded investment > 90 days and accruing	2,474	56
Consumer loans [Member] | Acquired loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
30-59 days past due	1,282	1,698
60-89 days past due	430	430
Greater than 90 days past due	2,170	2,126
Total past due	3,882	4,254
Current	199,092	382,286
Total Loans	202,974	386,540
Recorded investment > 90 days and accruing	47	1,009
Consumer loans [Member] | Covered loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	99,420	146,219
Total Loans	$ 99,420	$ 146,219