Derivative Instruments and Other Hedging Activities - Schedule of Outstanding Derivative Instruments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value of Derivatives
Derivative Asset	$ 104,151	$ 27,048
Derivative Liabilities	11,799	22,124
Notional Amount of Derivatives
Derivative assets	3,888,959	2,311,612
Derivative liabilities	3,313,072	1,991,559
Derivatives designated as hedging instruments
Fair Value of Derivatives
Derivative Asset	18,967	3,469
Derivative Liabilities	0	0
Notional Amount of Derivatives
Derivative assets	800,000	408,500
Derivative liabilities	108,500	0
Derivatives designated as hedging instruments | Customer swaps - downstream
Notional Amount of Derivatives
Derivative assets	800,000	408,500
Derivative liabilities	108,500	0
Derivatives designated as hedging instruments | Customer swaps - downstream | Other Assets
Fair Value of Derivatives
Derivative Asset	18,967	3,469
Derivatives designated as hedging instruments | Customer swaps - downstream | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	0	0
Derivatives not designated as hedging instruments
Notional Amount of Derivatives
Derivative assets	3,088,959	1,903,112
Derivative liabilities	3,204,572	1,991,559
Derivatives not designated as hedging instruments | Other Assets
Fair Value of Derivatives
Derivative Asset	85,184	23,579
Derivatives not designated as hedging instruments | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	11,799	22,124
Derivatives not designated as hedging instruments | Customer swaps - upstream
Notional Amount of Derivatives
Derivative assets	430,808	919,653
Derivative liabilities	2,237,542	701,257
Derivatives not designated as hedging instruments | Customer swaps - upstream | Other Assets
Fair Value of Derivatives
Derivative Asset	9	474
Derivatives not designated as hedging instruments | Customer swaps - upstream | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	5,055	191
Derivatives not designated as hedging instruments | Customer swaps - downstream
Notional Amount of Derivatives
Derivative assets	2,237,542	701,257
Derivative liabilities	430,808	919,653
Derivatives not designated as hedging instruments | Customer swaps - downstream | Other Assets
Fair Value of Derivatives
Derivative Asset	77,934	16,946
Derivatives not designated as hedging instruments | Customer swaps - downstream | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	1,680	17,812
Derivatives not designated as hedging instruments | Foreign exchange contracts
Notional Amount of Derivatives
Derivative assets	0	1,202
Derivative liabilities	0	1,202
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	0	18
Derivatives not designated as hedging instruments | Foreign exchange contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	0	18
Derivatives not designated as hedging instruments | Forward sales contracts
Notional Amount of Derivatives
Derivative assets	44,011	1,140
Derivative liabilities	230,998	143,179
Derivatives not designated as hedging instruments | Forward sales contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	420	630
Derivatives not designated as hedging instruments | Forward sales contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	986	750
Derivatives not designated as hedging instruments | Written and purchased options
Notional Amount of Derivatives
Derivative assets	268,590	229,333
Derivative liabilities	121,981	140,645
Derivatives not designated as hedging instruments | Written and purchased options | Other Assets
Fair Value of Derivatives
Derivative Asset	6,755	5,490
Derivatives not designated as hedging instruments | Written and purchased options | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	3,899	3,310
Derivatives not designated as hedging instruments | Other contracts
Notional Amount of Derivatives
Derivative assets	108,008	50,527
Derivative liabilities	183,243	85,623
Derivatives not designated as hedging instruments | Other contracts | Other Assets
Fair Value of Derivatives
Derivative Asset	66	21
Derivatives not designated as hedging instruments | Other contracts | Other Liabilities
Fair Value of Derivatives
Derivative Liabilities	$ 179	$ 43