Derivative Financial Instruments (Detail) - Nondesignated	Sep. 30, 2016 USD ($)
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	$ 3,741,722,000
Interest rate lock commitments
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	671,702,000
Treasury Options
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	440,000,000
Eurodollar Futures
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	175,000,000
Swaps
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	250,000,000
Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	1,255,010,000
Forward commitments to buy loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Derivative financial instruments held, notional amount	950,010,000
Other assets
Derivatives, Fair Value [Line Items]
Unrealized Gain	11,805,000	[1]
Other assets | Interest rate lock commitments
Derivatives, Fair Value [Line Items]
Unrealized Gain	6,934,000	[1]
Other assets | Eurodollar Futures
Derivatives, Fair Value [Line Items]
Unrealized Gain	12,000	[1]
Other assets | Swaps
Derivatives, Fair Value [Line Items]
Unrealized Gain	1,917,000	[1]
Other assets | Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Gain	56,000	[1]
Other assets | Forward commitments to buy loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Gain	2,886,000	[1]
Other liabilities
Derivatives, Fair Value [Line Items]
Unrealized Loss	5,599,000	[1]
Other liabilities | Treasury Options
Derivatives, Fair Value [Line Items]
Unrealized Loss	378,000	[1]
Other liabilities | Eurodollar Futures
Derivatives, Fair Value [Line Items]
Unrealized Loss	46,000	[1]
Other liabilities | Forward commitments to sell loans/mortgage-backed securities
Derivatives, Fair Value [Line Items]
Unrealized Loss	$ 5,175,000	[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.