STOCKHOLDERS' EQUITY AND EARNINGS PER SHARE (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jan. 16, 2014
Quarterly Dividends
Dividends for common stock declared (in dollars per share)	$ 0.20	$ 0.18	$ 0.60	$ 0.54
Common Stock
Class of Stock
Amount of stock repurchase approved by the Board of Directors	$ 100,000,000		$ 100,000,000
Quarterly Dividends
Dividends for common stock declared (in dollars per share)	$ 0.20
Common stock cash dividends paid	$ 29,100,000	$ 26,000,000	$ 87,100,000	$ 78,000,000
MetroCorp | Common Stock
Class of Stock
Number of shares under warrant	230,282		230,282
MetroCorp
Class of Stock
Number of shares under warrant					771,429