Loans and Allowance for Loan Losses - Loans, Net of Unearned Income (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Loans Receivable [Line Items]
Total covered loans	$ 331,137	$ 358,666
Total loans	12,527,937	12,324,817
Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total covered loans	14,269	23,390
Total loans	5,198,029	5,064,224
Construction and land development [Member]
Loans Receivable [Line Items]
Total covered loans	19,518	20,229
Total loans	978,798	915,541
Commercial real estate [Member]
Loans Receivable [Line Items]
Total covered loans	52,050	53,165
Total loans	3,069,316	3,042,841
Residential mortgages [Member]
Loans Receivable [Line Items]
Total covered loans	199,026	209,018
Total loans	1,720,307	1,720,614
Consumer [Member]
Loans Receivable [Line Items]
Total covered loans	46,274	52,864
Total loans	1,561,487	1,581,597
Originated loans [Member]
Loans Receivable [Line Items]
Total-excluding covered	9,924,364	9,494,132
Originated loans [Member] | Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial non-real estate	4,353,549	4,113,837
Originated loans [Member] | Construction and land development [Member]
Loans Receivable [Line Items]
Total-excluding covered-Construction and land development	824,837	752,381
Originated loans [Member] | Commercial real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial real estate	2,110,096	2,022,528
Originated loans [Member] | Residential mortgages [Member]
Loans Receivable [Line Items]
Total-excluding covered-Residential mortgages	1,228,170	1,196,256
Originated loans [Member] | Consumer [Member]
Loans Receivable [Line Items]
Total-excluding covered-Consumer	1,407,712	1,409,130
Acquired loans [Member]
Loans Receivable [Line Items]
Total-excluding covered	2,272,436	2,472,019
Acquired loans [Member] | Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial non-real estate	830,211	926,997
Acquired loans [Member] | Construction and land development [Member]
Loans Receivable [Line Items]
Total-excluding covered-Construction and land development	134,443	142,931
Acquired loans [Member] | Commercial real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial real estate	907,170	967,148
Acquired loans [Member] | Residential mortgages [Member]
Loans Receivable [Line Items]
Total-excluding covered-Residential mortgages	293,111	315,340
Acquired loans [Member] | Consumer [Member]
Loans Receivable [Line Items]
Total-excluding covered-Consumer	$ 107,501	$ 119,603