Inventories (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Mar. 31, 2012
Components of Inventories, valued using the first-in, first-out (FIFO) method
Raw materials	$ 104,607	$ 85,116
Work-in-process	135,971	123,723
Finished goods	307,881	270,628
Inventory Net	$ 548,459	$ 479,467