Earnings Per 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
Numerator:
Net income allocable to common stockholders	$ 16,911	$ 9,048
Denominator:
Denominator for basic earnings per share-weighted average shares	8,904	8,781
Effect of dilutive employee stock options and warrants	224	92
Denominator for diluted earnings per share-adjusted weighted average shares and assumed exercise	9,128	8,873
Basic:
Net income allocable to common stockholders	$ 1.90	$ 1.03
Diluted:
Net income allocable to common stockholders	$ 1.85	$ 1.02
Outstanding common stock equivalents having no dilutive effect	44	265