Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 29,193	$ 29,130	$ 57,731	$ 50,712
Basic weighted average common shares outstanding	144,380,873	139,093,641	142,028,751	138,996,110
Net effect of dilutive stock options, warrants, restricted stock and convertible debt	1,463,291	1,440,391	1,436,919	1,446,214
Diluted weighted average common shares outstanding	145,844,164	140,534,032	143,465,670	140,442,324
Basic earnings per share	$ 0.20	$ 0.21	$ 0.41	$ 0.36
Diluted earnings per share	$ 0.20	$ 0.21	$ 0.40	$ 0.36