Derivatives - Fair Value of Derivative Contracts (Detail) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		$ 51,557	$ 12,669
Derivative contracts, Liabilities		52,148	7,933
Notional Amounts	[1]	16,943,201	17,669,642
Foreign Exchange Swaps [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		896	801
Derivative contracts, Liabilities		2,075	2,846
Notional Amounts	[1]	577,988	407,600
Foreign Exchange/Commodities Options [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		137	4,416
Derivative contracts, Liabilities		33,849	130
Notional Amounts	[1]	3,704,117	2,442,200
Interest Rate Swaps [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets			242
Notional Amounts	[1]		12,092
Equity Options [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Liabilities			18
Notional Amounts	[1]		961,000
Forwards [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		35,917	4,262
Derivative contracts, Liabilities		1,647	1,483
Notional Amounts	[1]	1,835,242	642,802
Rate Lock Commitments [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		14,448	2,923
Derivative contracts, Liabilities		13,945	2,390
Notional Amounts	[1]	959,295	180,918
Futures [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts, Assets		159	25
Derivative contracts, Liabilities		632	1,066
Notional Amounts	[1]	$ 9,866,559	$ 13,023,030

[1] Notional amounts represent the sum of gross long and short derivative contracts, an indication of the volume of the Company’s derivative activity and does not represent anticipated losses.