Operating Interest Income and Operating Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating interest income:
Loans	$ 106,669	$ 139,501
Available-for-sale securities	64,005	105,661
Held-to-maturity securites	58,069	53,406
Margin receivables	54,447	47,990
Securities borrowed and other	16,870	15,703
Total operating interest income	300,060	362,261
Operating interest expense:
Securities sold under agreements to repurchase	(36,703)	(40,764)
FHLB advances and other borrowings	(16,930)	(25,422)
Deposits	(3,153)	(8,342)
Customer payables and other	(1,945)	(2,881)
Total operating interest expense	(58,731)	(77,409)
Net operating interest income	$ 241,329	$ 284,852