Stockholders' Equity - Narrative (Details) - USD ($)		12 Months Ended
	Mar. 17, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 28, 2008
February 2008 Board Authorization
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock authorized for stock repurchase program (in shares)					1,500,000
Shares repurchased (in shares)		0	0	0
Common stock left remaining to repurchase under the plan (in shares)		942,443
Aggregate stock repurchase amount		$ 5,000,000.0
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares converted (in shares)	3,175,584