Related Party Transactions (Details) - O&G [Member]	6 Months Ended
	Jun. 30, 2017 agreement
Purple Line Segment 2 Expansion Project [Member]
Related Party Transaction, Due from (to) Related Party [Abstract]
Number of joint ventures	1
Ownership percentage in joint venture	75.00%
Related party's ownership percentage in joint venture	25.00%
: Infrastructure Projects [Member]
Related Party Transaction, Due from (to) Related Party [Abstract]
Number of joint ventures	2
Infrastructure Project 1 [Member]
Related Party Transaction, Due from (to) Related Party [Abstract]
Construction project, percentage complete	99.00%
Infrastructure Project 2 [Member]
Related Party Transaction, Due from (to) Related Party [Abstract]
Construction project, percentage complete	100.00%