Stock-Based Compensation - Employee Stock Purchase Plan (Details) - Employee Stock Purchase Plan	12 Months Ended
Dec. 31, 2018 USD ($) shares
Stock-Based Compensation [Abstract]
Maximum fair value of common stock under ESPP	$ 25,000
Annual participation limit	$ 12,500
Shares purchased under the ESPP (in shares) \| shares	7,473
ESPP purchase price, percentage of fair market value	95.00%

Number of shares of capital stock issued (purchased by employees) in connection with an employee stock ownership plan.

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