Acquisitions (Details Textual) (USD $)	3 Months Ended								12 Months Ended			3 Months Ended	12 Months Ended
	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2013 Kvaerner North American Construction [Member]	Jun. 30, 2014 Kvaerner North American Construction [Member]	Dec. 21, 2013 Kvaerner North American Construction [Member]	Jun. 30, 2014 MXPB Power Partners [Member]	Dec. 21, 2013 MXPB Power Partners [Member]
Business Acquisition [Line Items]
Stock acquired, percent														100.00%
Acquisition price												$ 88,262,000
Goodwill	69,837,000				30,836,000				69,837,000	30,836,000	28,675,000	39,076,000
Tax deductible goodwill												30,700,000
Ownership interest in joint venture, percent															65.00%
Equity of joint venture acquired																2,000,000
Company's portion of joint venture equity acquired																1,300,000
Noncontrolling interest in joint venture	1,767,000				0				1,767,000	0					1,800,000	700,000
Revenues									1,263,089,000	892,574,000	739,046,000		154,800,000
Operating income	14,209,000	18,819,000	14,817,000	10,762,000	11,587,000	8,431,000	8,722,000	7,924,000	58,607,000	36,714,000	31,635,000		2,700,000
Acquisition-related expenses												2,000,000
Incremental intangible amortization expense									4,100,000
Depreciation expenses										1,300,000
Income from one-time tax settlement									$ 600,000