Stock Based Compensation - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified		12 Months Ended					1 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2011 Omnibus Incentive Plan	Dec. 31, 2011 Omnibus Incentive Plan Maximum	Dec. 31, 2011 Restricted Stock Year	Dec. 31, 2010 Restricted Stock	Dec. 31, 2009 Restricted Stock	Dec. 31, 2011 Stock Options Maximum Year	Jan. 31, 2011 Non Employee Directors, Plan	Dec. 31, 2011 Employee Stock Options	Dec. 31, 2010 Employee Stock Options	Dec. 31, 2009 Employee Stock Options	Dec. 31, 2011 Employee Stock Options Maximum Month	Dec. 31, 2011 Phantom Share Plan	Dec. 31, 2011 Phantom Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash-based award paid to a single participant in any calendar year		$ 2,000
Aggregate number of common stock for issuance under the plan		750,000
Shares granted to any single participant in any calandar year		50,000
Shares available for issuance under the plan	616,647
Vesting period			3 years									3 years
Term Period						10
Total shares issued under the deferred compensation plan for the period							4,058
Remaining deferred fees under the plan paid in the period							171
Options Exercised								3,475
Weighted-average exercise price of option exercised								$ 21.83
Options outstanding								2,425
Total intrinsic value of options exercised								346	250	944
Weighted-average remaining options contractual terms											12
Total unrecognized compensation expense, net			4,760
Unrecognized compensation expense, net, weighted average period			1.2
Weighted average grant date fair value				$ 68.80	$ 38.91
Total fair value of restricted stock vested			2,712	2,141	1,978
Units granted													21,565
Units vested													12,487
Units forfeited													2,844
Total fair value of units outstanding													$ 769