Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	$ 316,650	$ 414,263
Liability derivatives, Fair value	187,577	254,189
Derivatives not designated and qualifying as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	238,947	304,431
Liability derivatives, Fair value	185,139	253,702
Fair Value Hedges [Member] | Derivatives designated and qualifying as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	77,703	109,832
Liability derivatives, Fair value	2,438	487
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	76,249	102,875
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	1,387	6,120
Liability derivatives, Fair value	3,157	230
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	1,454	6,957
Liability derivatives, Fair value	2,438	487
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	16,732	7,616
Liability derivatives, Fair value	240	3,675
Interest rate contracts [Member] | Derivatives not designated and qualifying as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives, Fair value	203,779	274,864
Liability derivatives, Fair value	165,065	234,455
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	17,049	15,831
Liability derivatives, Fair value	$ 16,677	$ 15,342