Basis of Presentation (Textual) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2016	Sep. 30, 2017	Sep. 30, 2016
Basis Of Presentation [Line Items]
Shares used for employee taxes upon vesting of share awards		$ 674	$ 879
ASU 2016-09 [Member] | Reclassified from Operating Activities to Financing Activities [Member]
Basis Of Presentation [Line Items]
Shares used for employee taxes upon vesting of share awards			900
ASU 2016-15 [Member] | Reclassified from Operating Activities to Financing Activities [Member]
Basis Of Presentation [Line Items]
Debt prepayment costs			$ 53,400
Impairment Charges [Member]
Basis Of Presentation [Line Items]
Out-of-period error immaterial in current year	$ 1,200