Stock-Based Compensation (Restricted Stock Narrative) (Details)	12 Months Ended
Dec. 31, 2019 USD ($) $ / shares
Unvested restricted stock awards
Number of Shares
Fair value of restricted stock	$ 100,000
Unrecognized employee stock-based compensation	$ 18,900
Unrecognized employee stock-based compensation, period for recognition	4 months 24 days
Granted (in dollars per share) \| $ / shares	$ 0
Restricted Stock Units (RSUs)
Number of Shares
Fair value of restricted stock	$ 16,600,000
Unrecognized employee stock-based compensation	$ 26,000,000.0
Unrecognized employee stock-based compensation, period for recognition	2 years 1 month 6 days
Granted (in dollars per share) \| $ / shares	$ 5.09
Intrinsic value of nonvested unit	$ 65,900,000

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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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