Loans Receivable and Allowance for Loan Losses (Narrative) (Detail)	3 Months Ended		12 Months Ended
	Mar. 31, 2017 USD ($) borrower SecurityLoan Contract troubled_debt_restructuring	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($) borrower SecurityLoan Contract troubled_debt_restructuring	May 30, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Principal amount of nonaccrual loans	$ 40,500,000		$ 42,400,000
Loans less than 90 days past due	$ 5,200,000		$ 7,300,000
Number of loans 90 days past due and still accruing | Contract	0		0
Recorded Investment greater than 90 days accruing	$ 0		$ 0
Impaired loan defined floor limit (greater than)	$ 1,000,000.0
Impaired loans number | SecurityLoan	150		141
Impaired loans	$ 53,481,000		$ 52,019,000
Number of troubled debt restructurings | troubled_debt_restructuring	120		114
Loans and leases receivable, impaired, nonperforming, accrual of interest	$ 30,900,000		$ 29,900,000
Number of borrowers | borrower	116		110
Charge off, impaired loan	$ 0	$ 0
Weighted average modified interest rate	3.30%
Weighted average prior modification rate		3.61%
Interest income	$ 77,913,000	$ 73,974,000
Average balance of impaired loans	56,048,000		$ 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
Impaired Loans Troubled Debt Restructurings [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowances for loan losses	158,000
With Related Allowance For Loan Losses [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Allowances for loan losses	3,032,000		2,334,000
Loans With No Related Allowance [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans	30,038,000
Allowances for loan losses	0		0
Impaired financing receivable with no related allowance	30,000,000		31,800,000
Average balance of impaired loans	$ 32,494,000		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 loans			$ 31,809,000