Other Noncurrent Assets (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Mar. 31, 2013
Other noncurrent assets
Deposits	$ 4,144	[1]	$ 3,885	[1]
Deferred financing costs	28,575		16,080
Investment in affiliates	517		1,877
Capitalized software, net	3,494		3,993
Retirement plans	22,187		17,655
Other	9,482		7,559
Other noncurrent assets, total	$ 68,399		$ 51,049

[1] Deposits principally represent amounts held by beneficiaries as cash collateral for the Company’s contingent obligations with respect to certain environmental matters, workers' compensation insurance, and operating lease commitments.