Loans and Allowance for Loan Losses - Summary of Composition of Non-Accrual Loans by Portfolio Segment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	$ 89,901	$ 99,657
Commercial non-real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	15,133	13,330
Construction and land development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	11,051	16,700
Commercial real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	34,597	40,460
Residential mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	22,499	22,255
Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	6,621	6,912
Originated loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	71,488	74,313
Originated loans [Member] | Commercial non-real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	12,150	10,119
Originated loans [Member] | Construction and land development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	7,749	13,171
Originated loans [Member] | Commercial real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	27,753	32,772
Originated loans [Member] | Residential mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	19,157	13,449
Originated loans [Member] | Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	4,679	4,802
Acquired loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	15,093	21,800
Acquired loans [Member] | Commercial non-real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	2,983	3,209
Acquired loans [Member] | Construction and land development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	1,763	1,990
Acquired loans [Member] | Commercial real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	5,737	6,525
Acquired loans [Member] | Residential mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	2,946	8,262
Acquired loans [Member] | Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	1,664	1,814
Covered Loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	3,320	3,544
Covered Loans [Member] | Commercial non-real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans		2
Covered Loans [Member] | Construction and land development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	1,539	1,539
Covered Loans [Member] | Commercial real estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	1,107	1,163
Covered Loans [Member] | Residential mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	396	544
Covered Loans [Member] | Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Non-accrual loans	$ 278	$ 296