Nature of Operations and Basis of Presentation - Other Income (Deductions) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
Other Income and Expenses [Abstract]
Change in COLI policies	$ 1,300	$ 900	$ 5,700	$ 9,500
Interest income	590	497	2,695	838
Pipe replacement costs				(47)
Foreign transaction gain (loss)	(327)		(505)
Miscellaneous income and (expense)	709	215	(123)	(448)
Total other income (deductions)	$ 2,272	$ 1,612	$ 7,767	$ 9,843