Commitments and Contingencies - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Interest rate caps and swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	24,212	41,911
Derivatives designated as hedging instruments:
Derivative [Line Items]
Notional Amount	614,775	714,999
Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional Amount	1,800,238	1,322,305
Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	1,687,005	1,075,722
Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Notional Amount	113,233	246,583
Other Assets | Derivatives designated as hedging instruments:
Derivative [Line Items]
Other Assets	650	802
Other Assets | Derivatives not designated as hedging instruments:
Derivative [Line Items]
Other Assets	25,767	28,253
Other Assets | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Assets	25,696	25,285
Other Assets | Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	71	2,968
Other Liabilities | Derivatives designated as hedging instruments:
Derivative [Line Items]
Other Liabilities	718	16,627
Other Liabilities | Derivatives not designated as hedging instruments:
Derivative [Line Items]
Other Liabilities	23,612	27,450
Other Liabilities | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Liabilities	23,494	25,284
Other Liabilities | Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Other Liabilities	118	2,166
Fair value hedge | Derivatives designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	7,775	7,999
Fair value hedge | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	14,500
Fair value hedge | Other Assets | Derivatives designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Assets	0	0
Fair value hedge | Other Liabilities | Derivatives designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Liabilities	637	986
Cash flow hedge | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Notional Amount	607,000	707,000
Cash flow hedge | Other Assets | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Other Assets	650	802
Cash flow hedge | Other Liabilities | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Other Liabilities	$ 81	$ 15,641