Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative Assets - Fair Value	$ 107,747	$ 27,048
Derivative Liabilities - Fair Value	12,599	22,124
Designated as Hedging Instruments
Derivative [Line Items]
Derivative Assets - Fair Value	21,015	3,469
Derivative Liabilities - Fair Value	0	0
Other Assets | Designated as Hedging Instruments | Interest rate contracts
Derivative [Line Items]
Derivative Assets - Fair Value	21,015	3,469
Other Assets | Not Designated as Hedging Instruments
Derivative [Line Items]
Derivative Assets - Fair Value	86,732	23,579
Other Assets | Not Designated as Hedging Instruments | Interest rate contracts
Derivative [Line Items]
Derivative Assets - Fair Value	76,944	16,946
Other Assets | Not Designated as Hedging Instruments | Customer swaps - upstream
Derivative [Line Items]
Derivative Assets - Fair Value	24	474
Other Assets | Not Designated as Hedging Instruments | Foreign exchange contracts
Derivative [Line Items]
Derivative Assets - Fair Value	0	18
Other Assets | Not Designated as Hedging Instruments | Forward sales contracts
Derivative [Line Items]
Derivative Assets - Fair Value	146	630
Other Assets | Not Designated as Hedging Instruments | Written and purchased options
Derivative [Line Items]
Derivative Assets - Fair Value	9,574	5,490
Other Assets | Not Designated as Hedging Instruments | Other contracts
Derivative [Line Items]
Derivative Assets - Fair Value	44	21
Other Liabilities | Designated as Hedging Instruments | Interest rate contracts
Derivative [Line Items]
Derivative Liabilities - Fair Value	0	0
Other Liabilities | Not Designated as Hedging Instruments
Derivative [Line Items]
Derivative Liabilities - Fair Value	12,599	22,124
Other Liabilities | Not Designated as Hedging Instruments | Interest rate contracts
Derivative [Line Items]
Derivative Liabilities - Fair Value	1,760	17,812
Other Liabilities | Not Designated as Hedging Instruments | Customer swaps - upstream
Derivative [Line Items]
Derivative Liabilities - Fair Value	5,041	191
Other Liabilities | Not Designated as Hedging Instruments | Foreign exchange contracts
Derivative [Line Items]
Derivative Liabilities - Fair Value	0	18
Other Liabilities | Not Designated as Hedging Instruments | Forward sales contracts
Derivative [Line Items]
Derivative Liabilities - Fair Value	1,834	750
Other Liabilities | Not Designated as Hedging Instruments | Written and purchased options
Derivative [Line Items]
Derivative Liabilities - Fair Value	3,871	3,310
Other Liabilities | Not Designated as Hedging Instruments | Other contracts
Derivative [Line Items]
Derivative Liabilities - Fair Value	$ 93	$ 43