EARNINGS PER COMMON SHARE - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Numerator for basic and diluted earnings per share income available to common shareholders
Net income	$ 16,242	$ 15,618	$ 51,038	$ 48,798
Dividends on preferred stock	0	0	0	0
Income available to common shareholders	$ 16,242	$ 15,618	$ 51,038	$ 48,798
Denominator for basic earnings per share - weighted average shares	57,976,943	57,735,811	57,902,102	57,674,250
Employee stock awards	842,833	841,604	905,210	930,461
Warrants	120,403	76,684	123,258	95,241
Denominator for diluted earnings per share - adjusted weighted average shares	58,940,179	58,654,099	58,930,570	58,699,952
Earnings per share available to common shareholders
Basic	$ 0.28	$ 0.27	$ 0.88	$ 0.85
Diluted	$ 0.28	$ 0.27	$ 0.87	$ 0.83