Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease of cash outflow from financing activities	$ 119,843	$ (34,013)
Increase of cash outflow from operating activities	$ (78,929)	(96,699)
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease of cash outflow from financing activities		1,000
Increase of cash outflow from operating activities		$ 1,000