Amount of revenue earned from products sold or services provided under the terms of a contract, including, but not limited to, government contracts and construction contracts, classified as other.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Name:	us-gaap_ContractsRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Summary of Significant Accounting Principles - Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2016
Revenue, Major Customer [Line Items]
Contract revenues	$ 137,420	$ 140,301	$ 269,924
Customer One
Revenue, Major Customer [Line Items]
Contract revenues	$ 500			$ 12,300