STOCKHOLDERS' EQUITY AND EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jan. 16, 2014
Quarterly Dividends
Dividends for common stock declared (in dollars per share)	$ 0.20	$ 0.18	$ 0.40	$ 0.36
MetroCorp
Class of Stock
Number of shares under warrant					771,429
Common Stock
Class of Stock
Amount of stock repurchase approved by the Board of Directors	$ 100.0		$ 100.0
Quarterly Dividends
Dividends for common stock declared (in dollars per share)	$ 0.20
Common stock cash dividends paid	$ 29.0	$ 26.0	$ 58.0	$ 52.0
Common Stock | MetroCorp
Class of Stock
Number of shares under warrant	230,282		230,282