Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income from continuing operations	$ 68,563	$ 61,784	$ 49,447
Net income (loss) from discontinued operations	(189)	(1,715)	(1,743)
Gain on the sale of discontinued operations, net of tax benefit	7,642
Net income	$ 76,016	$ 60,069	$ 47,704
Basic weighted average shares outstanding	36,886	36,516	37,006
Income from continuing operations	$ 1.86	$ 1.69	$ 1.34
Income (loss) from discontinued operations	$ 0.20	$ (0.04)	$ (0.05)
Basic earnings per share	$ 2.06	$ 1.65	$ 1.29
Weighted average shares outstanding	36,886	36,516	37,006
Dilutive effect of stock options and restricted stock	1,002	1,300	2,602
Diluted weighted average shares outstanding	37,888	37,816	39,608
Income from continuing operations	$ 1.81	$ 1.64	$ 1.25
Income (loss) from discontinued operations	$ 0.20	$ (0.05)	$ (0.05)
Diluted earnings per share	$ 2.01	$ 1.59	$ 1.20
Common Stock Voting [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic weighted average shares outstanding	36,886	36,101	34,420
Weighted average shares outstanding	36,886	36,101	34,420
Common Stock Non-Voting [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic weighted average shares outstanding		415	2,586
Weighted average shares outstanding		415	2,586