GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)					3 Months Ended		6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2013 Premiums on acquired deposits	Jun. 30, 2012 Premiums on acquired deposits	Jun. 30, 2013 Premiums on acquired deposits	Jun. 30, 2012 Premiums on acquired deposits	Dec. 31, 2012 Premiums on acquired deposits
GOODWILL AND OTHER INTANGIBLE ASSETS
Goodwill	$ 337,438,000	$ 337,438,000	$ 337,438,000
Market capitalization	3,790,000,000
Total stockholders' equity	2,257,951,000	2,382,122,000	2,294,940,000	2,311,743,000
Premiums on Acquired Deposits
Gross carrying amount of premiums on acquired deposits					100,200,000		100,200,000		100,200,000
Accumulated amortization for premiums on acquired deposits					48,700,000		48,700,000		43,900,000
Amortization expense of premiums on acquired deposits					2,400,000	2,800,000	4,800,000	5,700,000
Estimated Future Amortization Expense of Premiums on Acquired Deposits
Remainder of the year					4,581,000		4,581,000
Year Ending December 31, 2014					8,454,000		8,454,000
Year Ending December 31, 2015					7,543,000		7,543,000
Year Ending December 31, 2016					6,634,000		6,634,000
Year Ending December 31, 2017					5,722,000		5,722,000
Thereafter					18,567,000		18,567,000
Total					$ 51,501,000		$ 51,501,000