CASH AND CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Composition of cash and cash equivalents
Cash and amounts due from banks	$ 933,050	$ 761,892
Cash equivalents:
Money market funds	3,526	621
Other short-term investments	386,530	668,672
Total cash and cash equivalents	1,323,106	1,431,185	1,333,949	1,099,084
Short-term investments
Balance at end of year	366,378	61,834
Average balance outstanding during the year	242,937	107,893
Maximum balance outstanding at any month-end	$ 367,283	$ 141,627
Weighted average interest rate at end of year (as a percent)	2.64%	1.34%