Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	$ 268,637	$ 338,855
Liability derivatives, Fair value	162,650	212,059
Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	222,901	264,876
Liability derivatives, Fair value	161,994	207,842
Fair Value Hedges [Member] | Derivatives Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	45,736	73,979
Liability derivatives, Fair value	656	4,217
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	43,892	73,251
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	533	754
Liability derivatives, Fair value	846	4,330
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	1,844	728
Liability derivatives, Fair value	656	4,217
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	10,282	17,396
Liability derivatives, Fair value	403	49
Interest Rate Contracts [Member] | Derivatives Not Designated and Qualifying as Hedging Instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	203,517	215,614
Liability derivatives, Fair value	153,723	173,513
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	8,569	31,112
Liability derivatives, Fair value	$ 7,022	$ 29,950