Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	$ 464,929	$ 268,637
Liability derivatives, Fair value	368,854	162,650
Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	431,210	222,901
Liability derivatives, Fair value	360,309	161,994
Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	33,719	45,736
Liability derivatives, Fair value	8,545	656
Interest Rate Swap Agreements [Member] | Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	33,648	43,892
Commitments to Sell Real Estate Loans [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	292	533
Liability derivatives, Fair value	7,720	846
Commitments to Sell Real Estate Loans [Member] | Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	71	1,844
Liability derivatives, Fair value	8,545	656
Mortgage-Related Commitments to Originate Real Estate Loans for Sale [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	21,431	10,282
Liability derivatives, Fair value	48	403
Interest Rate Contracts [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	401,512	203,517
Liability derivatives, Fair value	345,681	153,723
Foreign Exchange and Other Option and Futures Contracts [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	7,975	8,569
Liability derivatives, Fair value	$ 6,860	$ 7,022