Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage of vesting of share-based compensation awards.

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Share-Based Payments - Restricted Stock Narrative (Details) - USD ($) $ in Thousands			3 Months Ended	9 Months Ended	12 Months Ended				27 Months Ended
	Mar. 28, 2015	Mar. 11, 2015	Dec. 31, 2018	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					1 year
Allocated share-based compensation					$ 21,222	$ 16,127		$ 18,322
Time-based restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining unrecognized compensation cost related to nonvested awards			$ 13,700		$ 13,700
Weighted average remaining requisite service period					3 years
Time-based restricted stock awards \| Awards vesting on the one-year anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					25.00%
Award vesting period					1 year
Time-based restricted stock awards \| Awards vesting on the quarterly basis
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					6.25%
Award vesting period					3 years
Performance-based restricted stock awards, M356
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			1,812,758						949,620
Performance-based restricted stock awards, M356 \| Shares vesting upon FDA approval
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Performance-based restricted stock awards \| Awards vesting on the one-year anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period					1 year
Performance-based restricted stock awards \| Shares vesting upon FDA approval
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		50.00%
Performance-based restricted stock awards \| Awards vesting on the one-year anniversary of approval from FDA
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Award vesting period	1 year
Restricted stock awards and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					3,170,000
Allocated share-based compensation					$ 10,032	5,608		8,064
Forfeited (in shares)					707,000
Total fair value of shares of restricted stock vested					$ 13,600	$ 3,700		$ 7,600
Officers \| Time-based restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					1,357,505
Officers \| Restricted stock awards and restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)				1,785,600
Allocated share-based compensation					$ 1,100
Officers \| Restricted stock awards and restricted stock units \| Share-based Compensation Award, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage							25.00%
Officers \| Restricted stock awards and restricted stock units \| Share-based Compensation Award, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage							25.00%
Director \| Time-based restricted stock awards \| Awards vesting on the one-year anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					100.00%