Earnings per Common Share - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Earnings per common share—basic
Net income	$ 55,312	$ 41,660
Less: Preferred stock dividends	0	783
Net income allocable to common shareholders	55,312	40,877
Weighted-average common shares outstanding—basic	77,370	71,060
Basic earnings per common share	$ 0.71	$ 0.58
Earnings per common share—diluted
Net income	55,312	41,660
Dividends on convertible preferred stock	0	783
Interest on convertible debt, net of tax	1,236	1,209
Net income including assumed conversions	$ 56,548	$ 42,086
Weighted-average common shares outstanding—basic	77,370	71,060
Convertible notes weighted-average shares outstanding	15,000	15,000
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Preferred Stock	0	5,924
Options, restricted stock and other dilutive securities	802	213
Weighted-average common shares outstanding—diluted	93,172	92,197
Dilutive earnings per common share	$ 0.61	$ 0.47