Derivatives and Hedging Activities - Outstanding Interest Rate Swaptions and Derivative Instrument Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)
Changes in notional amount of derivative instruments [Roll Forward]
Notional amount as of January 1, 2016	$ 12,471,324,000
Additions	293,513,000
Settlement, Termination, Expiration or Exercise	(5,632,563,000)
Notional amount as of December 31, 2016	7,132,274,000
Interest Rate Swaps
Changes in notional amount of derivative instruments [Roll Forward]
Notional amount as of January 1, 2016	11,450,000,000
Additions	0
Settlement, Termination, Expiration or Exercise	(4,950,000,000)
Notional amount as of December 31, 2016	6,500,000,000
Interest Rate Swaptions
Changes in notional amount of derivative instruments [Roll Forward]
Notional amount as of January 1, 2016	300,000,000
Additions	0
Settlement, Termination, Expiration or Exercise	(300,000,000)
Notional amount as of December 31, 2016	0
Currency Forward Contracts
Changes in notional amount of derivative instruments [Roll Forward]
Notional amount as of January 1, 2016	76,324,000
Additions	293,513,000
Settlement, Termination, Expiration or Exercise	(307,529,000)
Notional amount as of December 31, 2016	62,308,000
Credit Derivatives
Changes in notional amount of derivative instruments [Roll Forward]
Notional amount as of January 1, 2016	645,000,000
Additions	0
Settlement, Termination, Expiration or Exercise	(75,034,000)
Notional amount as of December 31, 2016	$ 569,966,000