INVESTMENT SECURITIES (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Available-for-sale Securities	Jun. 30, 2011 Available-for-sale Securities	Mar. 31, 2012 Available-for-sale Securities	Mar. 31, 2011 Available-for-sale Securities
Other than Temporary Impairment, Credit Losses Recognized in Earnings
Beginning balance					$ 115,412,000	$ 124,340,000	$ 115,511,000	$ 115,243,000
Additional increases to the amount related to the credit loss for which an other-than-temporary impairment was previously recognized					99,000	464,000
Reduction for securities sold						(9,561,000)
Ending balance					115,511,000	115,243,000	115,511,000	115,243,000
Gross gains on sale of investment securities	26,300,000	1,700,000	28,000,000	11,900,000
Gross losses on sale of investment securities	26,200,000	563,000	27,400,000	8,300,000
Net income statement impact of gain on sale of investment securities	71,000	1,100,000	554,000	3,600,000
Net proceeds for sales of investment securities	$ 837,000,000	$ 215,000,000	$ 1,100,000,000	$ 527,800,000