Loans and Allowance for Loan Losses - Loans, Net of Unearned Income (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Loans Receivable [Line Items]
Total covered loans	$ 303,825	$ 358,666
Total loans	12,884,056	12,324,817
Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total covered loans	13,836	23,390
Total loans	5,393,691	5,064,224
Construction and land development [Member]
Loans Receivable [Line Items]
Total covered loans	17,199	20,229
Total loans	1,040,656	915,541
Commercial real estate [Member]
Loans Receivable [Line Items]
Total covered loans	46,611	53,165
Total loans	3,056,263	3,042,841
Residential mortgages [Member]
Loans Receivable [Line Items]
Total covered loans	189,570	209,018
Total loans	1,771,271	1,720,614
Consumer [Member]
Loans Receivable [Line Items]
Total covered loans	36,609	52,864
Total loans	1,622,175	1,581,597
Originated loans [Member]
Loans Receivable [Line Items]
Total-excluding covered	10,658,452	9,494,132
Originated loans [Member] | Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial non-real estate	4,610,696	4,113,837
Originated loans [Member] | Construction and land development [Member]
Loans Receivable [Line Items]
Total-excluding covered-Construction and land development	903,610	752,381
Originated loans [Member] | Commercial real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial real estate	2,173,006	2,022,528
Originated loans [Member] | Residential mortgages [Member]
Loans Receivable [Line Items]
Total-excluding covered-Residential mortgages	1,469,977	1,196,256
Originated loans [Member] | Consumer [Member]
Loans Receivable [Line Items]
Total-excluding covered-Consumer	1,501,163	1,409,130
Acquired loans [Member]
Loans Receivable [Line Items]
Total-excluding covered	1,921,779	2,472,019
Acquired loans [Member] | Commercial non-real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial non-real estate	769,159	926,997
Acquired loans [Member] | Construction and land development [Member]
Loans Receivable [Line Items]
Total-excluding covered-Construction and land development	119,847	142,931
Acquired loans [Member] | Commercial real estate [Member]
Loans Receivable [Line Items]
Total-excluding covered-Commercial real estate	836,646	967,148
Acquired loans [Member] | Residential mortgages [Member]
Loans Receivable [Line Items]
Total-excluding covered-Residential mortgages	111,724	315,340
Acquired loans [Member] | Consumer [Member]
Loans Receivable [Line Items]
Total-excluding covered-Consumer	$ 84,403	$ 119,603