Earnings Per 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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 31,634	$ 30,743	$ 89,365	$ 81,455
Basic weighted average common shares outstanding	144,759,887	139,228,812	142,949,134	139,074,244
Net effect of dilutive stock options, warrants, restricted stock and convertible debt	1,686,555	1,535,240	1,520,683	1,474,334
Diluted weighted average common shares outstanding	146,446,442	140,764,052	144,469,817	140,548,578
Basic earnings per share	$ 0.22	$ 0.22	$ 0.63	$ 0.59
Diluted earnings per share	$ 0.22	$ 0.22	$ 0.62	$ 0.58