CASH AND CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified					12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2011 Maximum D Y	Dec. 31, 2011 Minimum D
Composition of cash and cash equivalents
Term of original maturity to classify instruments as cash and cash equivalents (in days)					90
Cash and amounts due from banks	$ 761,892	$ 1,028,929
Cash equivalents:
Money market funds	621	15,008
Other short-term investments	668,672	290,012
Total cash and cash equivalents	1,431,185	1,333,949	1,099,084	878,853
Short-term investments
Term of original maturity to classify instruments as short-term investments					1	90
Balance at end of year	61,834	143,560
Average balance outstanding during the year	107,893	190,923
Maximum balance outstanding at any month-end	$ 141,627	$ 257,399
Weighted average interest rate at end of year (as a percent)	1.34%	1.45%