Additional Information Related to Equity-Based Compensation (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	$ 2,324	$ 1,739	$ 4,606	$ 3,377
Unrecognized Equity-Based Compensation	15,397		15,397
Weighted Average Years Remaining of Equity-Based Compensation
SARs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	601	618	1,202	1,226
Unrecognized Equity-Based Compensation	2,791		2,791
Weighted Average Years Remaining of Equity-Based Compensation	1 year 10 months 24 days		1 year 10 months 24 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	1,237	713	2,426	1,396
Unrecognized Equity-Based Compensation	7,814		7,814
Weighted Average Years Remaining of Equity-Based Compensation	2 years 2 months 12 days		2 years 2 months 12 days
DSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	96	87	186	246
Unrecognized Equity-Based Compensation	255		255
Weighted Average Years Remaining of Equity-Based Compensation	8 months 12 days		8 months 12 days
Equity-Based Compensation
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	1,934	1,418	3,814	2,868
Unrecognized Equity-Based Compensation	10,860		10,860
Weighted Average Years Remaining of Equity-Based Compensation
Non- Controlling Interest
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity-based compensation	390	321	792	509
Unrecognized Equity-Based Compensation	$ 4,537		$ 4,537
Weighted Average Years Remaining of Equity-Based Compensation	3 years 2 months 12 days		3 years 2 months 12 days