Summary of Significant Accounting Policies - Prior Period Adjustment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities	$ 5,928	$ 8,274
Net cash used for investing activities	$ (69,749)	(13,316)
Accounting Standards Update 2016-15
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities		8,274
Net cash used for investing activities		(13,316)
Accounting Standards Update 2016-15 | Activities as originally presented
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities		7,907
Net cash used for investing activities		(13,347)
Accounting Standards Update 2016-15 | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net cash provided by operating activities		367
Net cash used for investing activities		$ 31