Summary of Debt Outstanding (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Jun. 30, 2016	Mar. 31, 2016
Term Loan Facility
Debt [Line Items]
Outstanding borrowing	[1]	$ 300,000	$ 300,000
Revolving Line of Credit
Debt [Line Items]
Outstanding borrowing	[2],[3]	600,000	600,000
September 2013 Senior Unsecured Notes
Debt [Line Items]
Aggregate debt outstanding		$ 500,000	$ 500,000
Weighted average remaining life in years	[4]	7 years 2 months 12 days	7 years 4 months 24 days
Weighted average coupon rate on notes outstanding		4.86%	4.86%
Fair value of debt outstanding (Level 2)		$ 274,187	$ 342,746
August 2011 Senior Unsecured Notes
Debt [Line Items]
Aggregate debt outstanding		$ 165,000	$ 165,000
Weighted average remaining life in years	[4]	4 years 3 months 18 days	4 years 7 months 6 days
Weighted average coupon rate on notes outstanding		4.42%	4.42%
Fair value of debt outstanding (Level 2)		$ 108,620	$ 127,148
September 2010 Senior Unsecured Notes
Debt [Line Items]
Aggregate debt outstanding		$ 382,500	$ 382,500
Weighted average remaining life in years	[4]	3 years 9 months 18 days	4 years 1 month 6 days
Weighted average coupon rate on notes outstanding		4.35%	4.35%
Fair value of debt outstanding (Level 2)		$ 264,479	$ 302,832
May 2015 United States Dollar Denominated Borrowing Agreement
Debt [Line Items]
Fair value of debt outstanding (Level 2)	[5]	26,811	30,062
Amount outstanding	[5]	28,727	30,033
March 2015 United States Dollar Denominated Borrowing Agreement
Debt [Line Items]
Fair value of debt outstanding (Level 2)	[5]	25,266	27,027
Amount outstanding	[5]	$ 27,030	$ 27,030

[1] The fair value of the term loan agreement was $287.5 million at June 30, 2016 and approximated its carrying value at March 31, 2016.

[2] Fair values approximate carrying values because the borrowings bear interest at variable rates.

[3] The revolver was fully utilized at June 30, 2016 and March 31, 2016, respectively.

[4] Weighted average remaining life in years is based on stated maturities; however, all of the company’s indebtedness has been reclassified as current since March 31, 2016.

[5] Notes require semi-annual principal payments.