Derivative and Hedging Activities - Summary of Key Data Related to Interest Rate (Detail) - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 3,562,865,000	$ 2,893,041,000
Fair value included in other assets	108,149,000	53,202,000
Fair value included in other liabilities	100,817,000	51,605,000
Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	450,000,000	250,000,000
Fair value included in other liabilities	1,669,000	962,000
Designated as Hedging Instrument [Member] | Not for Trading Assets [Member] | Interest Rate Contracts [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair value included in other assets	10,022,000	3,178,000
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,470,266,000	1,262,964,000
Not Designated as Hedging Instrument [Member] | Trading Liabilities [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair value included in other liabilities	98,682,000	50,492,000
Not Designated as Hedging Instrument [Member] | Trading Assets [Member] | Interest Rate Swap [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair value included in other assets	$ 98,021,000	$ 49,999,000