Derivative Instruments	6 Months Ended
Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments Freestanding Derivative Forward Contracts The Company has international operations and is thus subject to foreign currency rate fluctuations. Approximately 99% of the Company's sales are U.S. Dollar denominated. However, a significant amount of the Company's expenses and liabilities are denominated in foreign currencies and subject to foreign currency rate fluctuations. To help manage the risk of changes in foreign currency rates, the Company periodically enters into derivative contracts comprised of foreign currency forward contracts to hedge its asset and liability foreign currency exposure and a portion of its foreign currency operating expenses. Foreign exchange rate fluctuations after the effects of hedging activity resulted in an immaterial amount and a net loss of $4.4 million for the three and six months ended September 30, 2018, respectively, compared to net gains of $5.0 million and $9.6 million for the three and six months ended September 30, 2017, respectively. As of September 30, 2018 and March 31, 2018, the Company had no foreign currency forward contracts outstanding. The Company recognized an immaterial amount of net losses and gains on foreign currency forward contracts in each of the three and six months ended September 30, 2018 and 2017. Gains and losses from changes in the fair value of these foreign currency forward contracts and foreign currency exchange rate fluctuations are credited or charged to other income (expense). The Company does not apply hedge accounting to its foreign currency derivative instruments. Commodity Price Risk The Company is exposed to fluctuations in prices for energy that it consumes, particularly electricity and natural gas. The Company also enters into variable-priced contracts for some purchases of electricity and natural gas, on an index basis. The Company seeks, or may seek, to partially mitigate these exposures through fixed-price contracts. These contracts meet the characteristics of derivative instruments, but generally qualify for the “normal purchases or normal sales” exception under authoritative guidance and require no mark-to-market adjustment.

Derivative Instruments

Freestanding Derivative Forward Contracts

The Company has international operations and is thus subject to foreign currency rate fluctuations. Approximately 99% of the Company's sales are U.S. Dollar denominated. However, a significant amount of the Company's expenses and liabilities are denominated in foreign currencies and subject to foreign currency rate fluctuations. To help manage the risk of changes in foreign currency rates, the Company periodically enters into derivative contracts comprised of foreign currency forward contracts to hedge its asset and liability foreign currency exposure and a portion of its foreign currency operating expenses. Foreign exchange rate fluctuations after the effects of hedging activity resulted in an immaterial amount and a net loss of $4.4 million for the three and six months ended September 30, 2018, respectively, compared to net gains of $5.0 million and $9.6 million for the three and six months ended September 30, 2017, respectively. As of September 30, 2018 and March 31, 2018, the Company had no foreign currency forward contracts outstanding. The Company recognized an immaterial amount of net losses and gains on foreign currency forward contracts in each of the three and six months ended September 30, 2018 and 2017. Gains and losses from changes in the fair value of these foreign currency forward contracts and foreign currency exchange rate fluctuations are credited or charged to other income (expense). The Company does not apply hedge accounting to its foreign currency derivative instruments.

Commodity Price Risk

The Company is exposed to fluctuations in prices for energy that it consumes, particularly electricity and natural gas. The Company also enters into variable-priced contracts for some purchases of electricity and natural gas, on an index basis. The Company seeks, or may seek, to partially mitigate these exposures through fixed-price contracts. These contracts meet the characteristics of derivative instruments, but generally qualify for the “normal purchases or normal sales” exception under authoritative guidance and require no mark-to-market adjustment.