Share-based Compensation - Summary of Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation	$ 6,561	$ 8,632	$ 10,492	$ 43,969
Continuing operations
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation	6,388	7,953	9,572	42,214
Continuing operations | Stock options, net of estimated forfeitures
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation	1,932	4,315	(3,333)	32,142
Continuing operations | Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation	4,456	3,638	12,905	10,072
Discontinued operations
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock compensation	$ 173	$ 679	$ 920	$ 1,755