Derivative financial instruments (Details 1) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	$ 643,449	$ 471,565
Liability derivatives, fair value	463,803	336,829
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	148,764	96,637
Liability derivatives, fair value	0	0
Commitments to sell real estate loans [Member] | Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	104	4,880
Liability derivatives, fair value	1,703	1,062
Commitments to sell real estate loans [Member] | Not Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	196	10,322
Liability derivatives, fair value	3,820	1,962
Mortgage-related commitments to originate real estate loans for sale [Member] | Not Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	7,997	2,827
Liability derivatives, fair value	60	583
Interest rate contracts [Member] | Not Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	460,533	345,632
Liability derivatives, fair value	434,844	321,461
Foreign exchange and other option and futures contracts [Member] | Not Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	25,855	11,267
Liability derivatives, fair value	23,376	11,761
Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	148,868	101,517
Liability derivatives, fair value	1,703	1,062
Not Designated as Hedging Instrument [Member]
Information about fair values of derivative instruments in consolidated balance sheet
Asset derivatives, fair value	494,581	370,048
Liability derivatives, fair value	$ 462,100	$ 335,767