SEGMENT INFORMATION (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Information about reportable segments
Net interest income	$ 53,909	$ 45,523
Provision for loan losses	1,644	1,050
Noninterest income	23,468	20,842
Amortization of intangible assets	1,086	901
Other operating expenses	48,317	42,415
Income before income taxes	26,330	21,999
Assets	6,912,458	5,549,372	6,488,275
Goodwill	345,050	297,692	345,050
Banking [Member]
Information about reportable segments
Net interest income	53,869	45,501
Provision for loan losses	1,644	1,050
Noninterest income	11,363	10,480
Amortization of intangible assets	804	700
Other operating expenses	38,517	34,549
Income before income taxes	24,267	19,682
Assets	6,887,276	5,525,773
Goodwill	334,554	287,411
Other [Member]
Information about reportable segments
Net interest income	40	22
Provision for loan losses	0	0
Noninterest income	12,679	10,843
Amortization of intangible assets	282	201
Other operating expenses	10,374	8,347
Income before income taxes	2,063	2,317
Assets	39,412	33,141
Goodwill	10,496	10,281
Elimination [Member]
Information about reportable segments
Net interest income	0	0
Provision for loan losses	0	0
Noninterest income	(574)	(481)
Amortization of intangible assets	0	0
Other operating expenses	(574)	(481)
Income before income taxes	0	0
Assets	(14,230)	(9,542)
Goodwill	$ 0	$ 0