Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Interest rate caps and swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	23,734	41,911
Derivatives designated as hedging instruments
Derivative [Line Items]
Other Assets	514	802
Other Liabilities	762	16,627
Notional Amount	614,832	714,999
Derivatives designated as hedging instruments | Cash flow hedge | Interest rate caps and swaps
Derivative [Line Items]
Other Assets	514	802
Other Liabilities	0	15,641
Notional Amount	607,000	707,000
Derivatives designated as hedging instruments | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Other Assets	0	0
Other Liabilities	762	986
Notional Amount	7,832	7,999
Derivatives not designated as hedging instruments
Derivative [Line Items]
Other Assets	26,182	28,253
Other Liabilities	23,106	27,450
Notional Amount	1,392,610	1,322,305
Derivatives not designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Other Assets	25,999	25,285
Other Liabilities	22,972	25,284
Notional Amount	1,279,055	1,075,722
Derivatives not designated as hedging instruments | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	183	2,968
Other Liabilities	134	2,166
Notional Amount	$ 113,555	$ 246,583