GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	12 Months Ended				12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2013 Premiums on acquired deposits	Dec. 31, 2012 Premiums on acquired deposits	Dec. 31, 2011 Premiums on acquired deposits
GOODWILL AND OTHER INTANGIBLE ASSETS
Goodwill	$ 337,438,000		$ 337,438,000
Market capitalization	4,810,000,000
Total stockholders' equity	2,364,225,000	2,382,122,000	2,311,743,000	2,113,931,000
Number of business divisions	3
Number of operating segments	3
Period for which the company provided a net income projection under the income approach to determine the fair value of the reporting units	3 years
Goodwill impairment	0
Changes in carrying amount of goodwill
Balance, beginning of year	337,438,000		337,438,000
Balance, end of year	337,438,000		337,438,000
Premiums on Acquired Deposits
Gross carrying amount of premiums on acquired deposits					100,200,000	100,200,000
Accumulated amortization for premiums on acquired deposits					53,300,000	43,900,000
Amortization expense of premiums on acquired deposits					9,400,000	10,900,000	12,300,000
Estimated Future Amortization Expense of Premiums on Acquired Deposits
2014	8,454,000
2015	7,543,000
2016	6,634,000
2017	5,722,000
2018	4,908,000
Thereafter	13,659,000
Total	$ 46,920,000