Loans Receivable and Allowance for Loan Losses (Narrative) (Detail)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($) Contract	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) Contract SecurityLoan troubled_debt_restructuring borrower	Jun. 30, 2016 USD ($) SecurityLoan	Jun. 30, 2017 USD ($) Contract SecurityLoan	Dec. 31, 2016 USD ($) Contract SecurityLoan troubled_debt_restructuring borrower	Jun. 30, 2016 SecurityLoan	May 30, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of nonaccrual loans	$ 38,900,000		$ 38,900,000		$ 38,900,000	$ 42,400,000
Loans less than 90 days past due	$ 724,000		$ 724,000		$ 724,000	$ 7,300,000
Number of loans 90 days past due and still accruing | Contract	0		0		0	0
Recorded Investment greater than 90 days accruing	$ 0		$ 0		$ 0	$ 0
Impaired loan defined floor limit (greater than)	1,000,000.0		$ 1,000,000.0		1,000,000.0
Impaired loans number | SecurityLoan			150			141
Impaired loans	52,670,000		$ 52,670,000		52,670,000	$ 52,019,000
Number of troubled debt restructurings | troubled_debt_restructuring			121			114
Number of borrowers | borrower			117			110
Loans and leases receivable, impaired, nonperforming, accrual of interest	31,300,000		$ 31,300,000		$ 31,300,000	$ 29,900,000
Charge off, impaired loan	0	$ 0	$ 1,200,000	$ 0
Weighted average modified interest rate		3.74%		4.01%
Weighted average prior modification rate		3.87%		3.90%
Number of payment defaults for loans modified as TDRs | SecurityLoan			0	1	0		0
Average balance of impaired loans			$ 53,854,000			52,002,000
Team Capital Bank [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of acquired loans								$ 5,200,000
Balance of PCI loans	1,300,000		1,300,000		$ 1,300,000	1,300,000
Impaired Loans Troubled Debt Restructurings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowances for loan losses		$ 0		$ 216,000
With Related Allowance For Loan Losses [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowances for loan losses	4,104,000		4,104,000		4,104,000	2,334,000
Loans With No Related Allowance [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowances for loan losses	0		0		0	0
Impaired financing receivable with no related allowance	$ 33,670,000		33,670,000		$ 33,670,000
Average balance of impaired loans			$ 34,680,000			26,971,000
Loans With No Related Allowance [Member] | No Allowance For Loan Losses Required [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired financing receivable with no related allowance						$ 31,809,000