Stockholders' Equity - Amended and Restated Certificate of Incorporation (Details)	12 Months Ended
	Dec. 31, 2018 class shares	Dec. 31, 2017 shares
Stockholders' Equity
Common stock, authorized (in shares) | shares	150,000,000	150,000,000
Preferred stock, authorized (in shares) | shares	10,000,000
Board of Directors, number of classes | class	3
Term of Board member	3 years
Number of classes elected at each annual meeting | class	1
Minimum
Stockholders' Equity
Affirmative vote of all then-outstanding shares of capital stock for removal of directors (as a percent)	75.00%