Stock Compensation - Additional Information (Detail) (USD $)	12 Months Ended											1 Months Ended		12 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Former Executives	Dec. 31, 2011 Former Executives Maximum	Dec. 31, 2010 Former Chief Executive Officer	Dec. 31, 2010 Former Chief Executive Officer Common Stock	Dec. 31, 2012 Restricted Stock	Dec. 31, 2011 Restricted Stock	Dec. 31, 2010 Restricted Stock	Dec. 31, 2010 Restricted Stock Former Chief Executive Officer	Aug. 31, 2012 Restricted Stock Units (RSUs)	Apr. 30, 2012 Restricted Stock Units (RSUs)	Dec. 31, 2012 Restricted Stock Units (RSUs)	Nov. 30, 2012 Stock Appreciation Rights (SARs)	Aug. 31, 2012 Stock Appreciation Rights (SARs)	Dec. 31, 2012 Stock Appreciation Rights (SARs)	Dec. 31, 2012 Stock Incentive Plan, 2011, Beginning in June 2011	Dec. 31, 2012 Stock Incentive, 2002 to December 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock remain available for future grant under the 2011 Plan																		1,153,000
Share based compensation granted under plan vest period													2 years					4 years	3 years
Underlying shares vesting on each anniversary of grant																			33.33%
Term of award																			10 years
Underlying shares vesting on the first anniversary of the grant																		25.00%
Underlying shares monthly vesting percentage after the first anniversary of the grant																		2.08%
Weighted-average fair value per share of stock-based awards, granted to employees	$ 9.54	$ 6.12	$ 6.66									$ 10.08	$ 5.40
Intrinsic value of stock options exercised	$ 5,022,000	$ 82,000	$ 976,000
Grant date fair value of stock options that vested	3,749,000	2,777,000	2,666,000					42,000	26,000	219,000
Stock issued during period, value stock options exercised	3,780,000	166,000	2,012,000
Expected dividend yield	0.00%	0.00%	0.00%
Granted, shares								4,998	5,000	3,333		7,500	32,377	39,877	100,000	70,000	170,000
Stock-based compensation expense recognized	3,078,080	3,129,000	3,169,000	526,000		1,181,000		38,000	22,000	26,000
Exercise price of SARs															$ 23.85	$ 10.08
Unrecognized compensation cost related to nonvested share-based compensation arrangements granted, including stock options and restricted stock	17,034,000
Unrecognized compensation costs expected to be recognized period	3 years 2 months 12 days
Stock compensation expense related to separation and acceleration vesting				$ 1,284,000		$ 1,384,000
Extended exercise period of existing stock options					1 year
Unvested options previously granted, vested number							194,472				19,417