Net Income (Loss) Per Common Share From Continuing Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss) from continuing operations	$ 189,156	$ 35,574	$ 359,743	$ (73,651)
Weighted average common shares outstanding	233,299,000	215,524,000	231,364,000	214,935,000
Dilutive effect of stock options and RSUs	4,464,000	4,465,000	4,490,000	0
Weighted average common and potential common shares outstanding	244,767,000	233,960,000	243,835,000	214,935,000
Income from continuing operations, per basic share (in USD per share)	$ 0.81	$ 0.17	$ 1.55	$ (0.34)
Income from continuing operations, per diluted share (in USD per share)	$ 0.77	$ 0.15	$ 1.48	$ (0.34)
Antidilutive securities excluded from computation of earnings per share, amount			4,312,066
2007 Junior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of debt	677,848	13,971,278	2,403,261	0
Antidilutive securities excluded from computation of earnings per share, amount				13,068,545
Interest rate of subordinated convertible debentures	2.125%		2.125%
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 23.58	$ 24.07	$ 23.64	$ 24.15
2015 Senior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive effect of debt	6,326,313		5,577,932
Interest rate of subordinated convertible debentures	1.625%		1.625%
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 64.06	65.38	$ 64.21	65.60
2017 Senior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate of subordinated convertible debentures	1.625%		1.625%
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 99.90	0.00	$ 100.13	0.00
2017 Junior Subordinated Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Interest rate of subordinated convertible debentures	2.25%		2.25%
Weighted average conversion price per share used in calculating dilutive effect of convertible debt (amount per share)	$ 98.15	$ 0.00	$ 98.37	$ 0.00

The weighted average price per share of the conversion feature embedded in the debt instrument.

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