Stock-based Compensation - Summary of Stock-based Compensation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 2,683	$ 393	$ 4,437	$ 1,362
Restricted shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,246	(41)	3,306	254
SARs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	434	415	1,116	1,019
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3	$ 19	$ 15	$ 89