Comprehensive Income (Loss) and Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012
Components of comprehensive income (loss)
Net income (loss)	$ (24,921)	$ 14,318	$ (42,674)	$ 46,167
Currency translation gain (loss)	3,907	(11,592)	(4,059)	(8,487)
Total comprehensive income (loss)	(22,490)	2,735	(48,036)	37,735
The components of Accumulated other comprehensive income on the Condensed Consolidated Balance Sheets
Foreign currency translation gain	14,048		14,048		18,107
Total Accumulated other comprehensive income	6,658		6,658		12,020
Defined benefit pension plans
Components of comprehensive income (loss)
Amortization of defined benefit pension and postretirement benefit plans	(1,244)	100	(1,142)	216
The components of Accumulated other comprehensive income on the Condensed Consolidated Balance Sheets
Defined benefit postretirement plan and defined benefit pension plans adjustments	(9,224)		(9,224)		(8,082)
Defined benefit postretirement pension plan
Components of comprehensive income (loss)
Amortization of defined benefit pension and postretirement benefit plans	(232)	(91)	(161)	(161)
The components of Accumulated other comprehensive income on the Condensed Consolidated Balance Sheets
Defined benefit postretirement plan and defined benefit pension plans adjustments	$ 1,834		$ 1,834		$ 1,995