STOCKHOLDERS' EQUITY AND EARNINGS PER SHARE (Details) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		6 Months Ended		0 Months Ended		0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended	6 Months Ended
	Jan. 17, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jan. 17, 2014 MetroCorp	Jan. 16, 2014 MetroCorp	May 01, 2013 Series A Non-Cumulative Perpetual Convertible Preferred Stock	Apr. 30, 2008 Series A Non-Cumulative Perpetual Convertible Preferred Stock	Jul. 17, 2013 Common Stock	Apr. 30, 2014 Common Stock	Jun. 30, 2014 Common Stock	Jun. 30, 2014 Common Stock
Class of Stock
Number of shares issued during the period									200,000
Preferred stock dividend rate (as a percent)									8.00%
Preferred stock liquidation preference (in dollars per share)									$ 1,000
Proceeds from issuance of convertible preferred stock									$ 194.1
Preferred shares converted								85,710
Common stock issued on conversion of convertible preferred stock								5,594,080
Final consideration (in shares)				5,583,093		5,583,093
Final consideration in cash						89.4
Number of outstanding warrants (in shares)		230,282		230,282			771,429
Common stock equivalent to assumed obligation of acquiree's unexercised warrant (in shares)	230,282
Amount of stock repurchase approved by the Board of Directors										100.0
Purchase of treasury stock pursuant to the Stock Repurchase Program, shares					8,026,807
Weighted average price of shares repurchased (in dollars per share)					$ 24.89
Total cost of repurchase of treasury shares			200.0		200.0
Quarterly Dividends
Dividend per share (in dollars per share)		$ 0.18	$ 0.15	$ 0.36	$ 0.30						$ 0.18
Common stock cash dividends paid												$ 26.0	$ 52.0