Earnings per Share - Schedule of Computation of Basic and Diluted EPS (Detail) (USD $) In Thousands, except Per 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	$ 21,302	$ 11,642	$ 50,270	$ 25,459
Noncontrolling interests	(213)		164
Allocation of earnings to preferred stockholders				(64)
Net Income Attributable to Common Stockholders	$ 21,089	$ 11,642	$ 50,434	$ 25,395
Shares (in thousands):
Basic: Weighted-average number of shares outstanding	7,995	7,843	7,879	7,692
Plus: Incremental shares from assumed conversion of dilutive instruments	232	274	246	363
Diluted: Weighted-average number of shares outstanding	8,227	8,117	8,125	8,055
Earnings per share - Basic	$ 2.64	$ 1.48	$ 6.40	$ 3.30
Earnings per share - Diluted	$ 2.56	$ 1.43	$ 6.21	$ 3.15