Acquisitions (Details Textual) - USD ($) $ in Thousands			3 Months Ended								12 Months Ended
	Aug. 22, 2014	Dec. 21, 2013	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2013
Business Acquisition [Line Items]
Goodwill			$ 71,518				$ 69,837				$ 71,518	$ 69,837	$ 30,836
Noncontrolling interest in joint venture			(8,742)				1,767				(8,742)	1,767
Revenues											1,343,135	1,263,089	892,574
Operating income			$ 18,374	$ (14,448)	$ (3,671)	$ 8,547	$ 14,209	$ 18,819	$ 14,817	$ 10,762	$ 8,802	58,607	36,714
HDB, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Aug. 22, 2014
Acquisition price						$ 5,600
Kvaerner North American Construction [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 51,607
Stock acquired, percent		100.00%
Acquisition price		$ 88,262							88,262
Goodwill		39,295							$ 39,295
Tax deductible goodwill		30,700
Acquisition-related expenses													2,000
Incremental intangible amortization expense												4,100	4,100
Depreciation expenses												1,300	$ 1,300
Income from one-time tax settlement												$ 600
MXPB Power Partners [Member]
Business Acquisition [Line Items]
Ownership interest in joint venture, percent			65.00%								65.00%
Equity of joint venture acquired		2,000
Company's portion of joint venture equity acquired		1,300
Noncontrolling interest in joint venture		$ 700