Stock Incentive Plans - Restricted Stock (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance of common stock	$ 10,000	$ 2,743	$ 0
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of common stock upon exercise of options (in shares)					30,317
Stock issued (in shares)				2,564
Proceeds from issuance of common stock				$ 100