Summary of Significant Accounting Principles - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue, Major Customer [Line Items]
Contract revenues	$ 164,017		$ 137,061	$ 433,941	$ 304,607
Customer One
Revenue, Major Customer [Line Items]
Contract revenues		$ 11,000