Stock Based Compensation - Additional Information (Detail) (USD $)	3 Months Ended				9 Months Ended	3 Months Ended					12 Months Ended		12 Months Ended		3 Months Ended		9 Months Ended	12 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2013 offering_period	Mar. 31, 2012	Mar. 31, 2013 Employee Stock Purchase Plan [Member]	Sep. 30, 2011 Employee Stock Purchase Plan [Member]	Sep. 30, 2011 Employee Stock Purchase Plan [Member]	Mar. 31, 2013 Stock Options [Member]	Mar. 31, 2013 Stock Option [Member]	Mar. 31, 2012 Stock Option [Member]	Mar. 31, 2013 Performance-Based Restricted Stock [Member]	Mar. 31, 2012 Performance-Based Restricted Stock [Member]	Dec. 31, 2010 Performance-Based Restricted Stock [Member]	Dec. 31, 2011 Performance-Based Restricted Stock [Member]	Dec. 31, 2010 Performance-Based Restricted Stock [Member] Minimum [Member]	Dec. 31, 2010 Performance-Based Restricted Stock [Member] Maximum [Member]	Mar. 31, 2013 Time Based Restricted Stock [Member]	Mar. 31, 2012 Time Based Restricted Stock [Member]	Sep. 30, 2011 Time Based Restricted Stock [Member]	Dec. 31, 2012 Time Based Restricted Stock [Member]	Mar. 31, 2013 Deferred Stock Units [Member]	Sep. 30, 2011 Deferred Stock Units [Member]	Sep. 30, 2011 Deferred Stock Units [Member]
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	5 years 10 months 25 days	5 years 10 months 25 days							3 years
Stock options, contractual term						10 years
Expected volatility		47.70%							37.10%
Stock options, expected dividend yield		1.43%							0.40%
Stock-based compensation, approximate forfeitures rate						3.00%
Compensation expense (income)	$ 688,000	$ 1,442,000	$ 100,000	$ 100,000			$ 300,000	$ 700,000	$ 100,000	$ 100,000					$ 300,000	$ 500,000			$ 0	$ 0
Options exercised, total intrinsic value	1,600,000
Total amount of cash received from exercise of options	$ 3,400,000
Restricted stock award program, measurement period											three
Restricted stock award program, awarded shares as a percentage of the original award amount													0.00%	200.00%
Restricted stock award program, payment of award as percentage of target												200.00%
Restricted stock award program, vesting period																		3 years
Employee stock purchase plan, number of offering	2
Employee stock purchase plan, offering period	6 months
Employee stock purchase plan, purchase price discount			15.00%
Expected dividend yield	0.00%	0.00%				0.00%