Commitments and Contingencies - Consolidated Statements of Financial Condition Related to Fair Value of Derivative Financial Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Interest rate caps and swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	22,907	24,212
Derivatives designated as hedging instruments:
Derivative [Line Items]
Notional Amount	339,536	614,775
Derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional Amount	3,495,825	1,800,238
Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	3,390,578	1,687,005
Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Notional Amount	105,247	113,233
Other Assets | Derivatives designated as hedging instruments:
Derivative [Line Items]
Other Assets	0	650
Other Assets | Derivatives not designated as hedging instruments:
Derivative [Line Items]
Other Assets	48,979	25,767
Other Assets | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Assets	48,642	25,696
Other Assets | Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	337	71
Other Liabilities | Derivatives designated as hedging instruments:
Derivative [Line Items]
Other Liabilities	374	718
Other Liabilities | Derivatives not designated as hedging instruments:
Derivative [Line Items]
Other Liabilities	23,307	23,612
Other Liabilities | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Other Liabilities	22,533	23,494
Other Liabilities | Derivatives not designated as hedging instruments: | Mortgage banking derivatives
Derivative [Line Items]
Other Liabilities	774	118
Cash flow hedge | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Notional Amount	332,000	607,000
Cash flow hedge | Other Assets | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Other Assets	0	650
Cash flow hedge | Other Liabilities | Derivatives designated as hedging instruments: | Interest rate caps and swaps
Derivative [Line Items]
Other Liabilities	27	81
Fair value hedge | Derivatives designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	7,536	7,775
Fair value hedge | Derivatives not designated as hedging instruments: | Interest rate swaps
Derivative [Line Items]
Notional Amount	10,400
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	$ 347	$ 637