Loans - Summary of Composition of Non-Accrual Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	$ 159,713	$ 79,537
Commercial Non-Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	88,743	15,511
Construction and Land Development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	17,294	7,565
Commercial Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	20,816	28,619
Residential Mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	23,799	22,094
Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	9,061	5,748
Originated Loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	156,721	71,296
Originated Loans [Member] | Commercial Non-Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	88,743	15,511
Originated Loans [Member] | Construction and Land Development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	17,294	6,462
Originated Loans [Member] | Commercial Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	17,824	22,047
Originated Loans [Member] | Residential Mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	23,799	21,702
Originated Loans [Member] | Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	9,061	5,574
Acquired Loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	2,992	6,139
Acquired Loans [Member] | Commercial Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans	$ 2,992	6,139
FDIC Acquired Loans [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans		2,102
FDIC Acquired Loans [Member] | Construction and Land Development [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans		1,103
FDIC Acquired Loans [Member] | Commercial Real Estate [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans		433
FDIC Acquired Loans [Member] | Residential Mortgages [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans		392
FDIC Acquired Loans [Member] | Consumer [Member]
Nonaccrual Loans By Portfolio [Line Items]
Nonaccrual loans		$ 174