Reportable Segments (Details) (USD $)	3 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012
Reportable Segments
Number of reportable segments	2
Summarized financial information concerning the Company's reportable segments
Revenue	$ 1,953,875,000	$ 2,017,272,000
Revenue, net of other direct costs	1,151,500,000	1,245,000,000
Gross profit	78,198,000	78,118,000
Equity in earnings of joint ventures	36,083,000	5,915,000
General and administrative expenses	(23,845,000)	(22,102,000)
Operating income (loss)	90,436,000	61,931,000
Gross profit as a % of revenue	4.00%	3.90%
Gross profit as a % of revenue, net of other direct costs	6.80%	6.30%
Corporate
Summarized financial information concerning the Company's reportable segments
General and administrative expenses	(23,900,000)	(22,100,000)
Operating income (loss)	(23,900,000)	(22,100,000)
Professional Technical Services
Summarized financial information concerning the Company's reportable segments
Revenue	1,770,200,000	1,771,200,000
Revenue, net of other direct costs	1,041,600,000	1,093,800,000
Gross profit	60,000,000	69,300,000
Equity in earnings of joint ventures	34,100,000	5,100,000
Operating income (loss)	94,100,000	74,400,000
Gross profit as a % of revenue	3.40%	3.90%
Gross profit as a % of revenue, net of other direct costs	5.80%	6.30%
Management Support Services
Summarized financial information concerning the Company's reportable segments
Revenue	183,700,000	246,100,000
Revenue, net of other direct costs	109,900,000	151,200,000
Gross profit	18,200,000	8,800,000
Equity in earnings of joint ventures	2,000,000	800,000
Operating income (loss)	$ 20,200,000	$ 9,600,000
Gross profit as a % of revenue	9.90%	3.60%
Gross profit as a % of revenue, net of other direct costs	16.60%	5.80%