Derivative Financial Instruments (Detail) - Nondesignated	Sep. 30, 2017 USD ($)
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	$ 765,886,000
Interest rate lock commitments
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	55,886,000
Treasury Options
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	20,000,000
Eurodollar Futures
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	20,000,000
Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	365,000,000
Forward commitments to buy loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	305,000,000
Other assets
Derivatives, Fair Value [Line Items]
Unrealized Gain	1,106,000	[1]
Other assets | Interest rate lock commitments
Derivatives, Fair Value [Line Items]
Unrealized Gain	269,000	[1]
Other assets | Eurodollar Futures
Derivatives, Fair Value [Line Items]
Unrealized Gain	1,000	[1]
Other assets | Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Gain	836,000	[1]
Other liabilities
Derivatives, Fair Value [Line Items]
Unrealized Loss	1,466,000	[1]
Other liabilities | Treasury Options
Derivatives, Fair Value [Line Items]
Unrealized Loss	144,000	[1]
Other liabilities | Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Loss	461,000	[1]
Other liabilities | Forward commitments to buy loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Loss	$ 861,000	[1]

[1] Derivatives in a net gain position are recorded as "Other assets" and derivatives in a net loss position are recorded as "Other liabilities" in the Consolidated Statements of Condition.