Derivative Instruments and Hedging Activities - Balance Sheet Disclosures (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Interest rate caps and swaps
Derivative [Line Items]
Other Assets	$ 0	$ 0
Other Liabilities	29,896	24,212
Derivatives designated as hedging instruments
Derivative [Line Items]
Other Assets	644	650
Other Liabilities	626	718
Notional Amount	614,717	614,775
Derivatives designated as hedging instruments | Cash flow hedge | Interest rate caps and swaps
Derivative [Line Items]
Other Assets	644	650
Other Liabilities	119	81
Notional Amount	607,000	607,000
Derivatives designated as hedging instruments | Fair value hedge | Interest rate swaps
Derivative [Line Items]
Other Assets	0	0
Other Liabilities	507	637
Notional Amount	7,717	7,775
Derivatives not designated as hedging instruments
Derivative [Line Items]
Other Assets	25,338	25,767
Other Liabilities	29,493	23,612
Notional Amount	2,840,885	1,800,238
Derivatives not designated as hedging instruments | Interest rate swaps
Derivative [Line Items]
Other Assets	25,132	25,696
Other Liabilities	29,270	23,494
Notional Amount	2,731,500	1,687,005
Derivatives not designated as hedging instruments | Mortgage banking derivatives
Derivative [Line Items]
Other Assets	206	71
Other Liabilities	223	118
Notional Amount	$ 109,385	$ 113,233