Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 190,515	$ 488,777
Accounts receivable, net of allowances of $6,174 and $5,215	1,812,539	1,439,115
Costs and estimated earnings in excess of billings on uncompleted contracts	290,447	213,478
Inventories	38,921	31,877
Prepaid expenses and other current assets	221,554	140,071
Total current assets	2,553,976	2,313,318
Property and equipment, net of accumulated depreciation of $739,545 and $631,939	1,480,128	1,205,608
Other assets, net	85,842	285,725
Other intangible assets, net of accumulated amortization of $255,858 and $223,355	260,593	207,877
Goodwill	1,931,485	1,780,717
Total assets	6,312,024	5,793,245
Current Liabilities:
Current maturities of long-term debt and short-term borrowings	8,876	1,181
Accounts payable and accrued expenses	877,336	802,180
Billings in excess of costs and estimated earnings on uncompleted contracts	251,113	239,106
Total current liabilities	1,137,325	1,042,467
Long-term debt and notes payable, net of current maturities	72,489	1,053
Deferred income taxes	300,516	244,256
Insurance and other non-current liabilities	276,154	264,150
Total liabilities	1,786,484	1,551,926
Commitments and Contingencies
Equity:
Common stock, value	2	2
Additional paid-in capital	3,592,906	3,416,585
Retained earnings	1,366,791	1,070,077
Accumulated other comprehensive income (loss)	(123,290)	(37,236)
Treasury stock, 15,374,866 and 12,026,030 common shares, at cost	(321,936)	(215,240)
Total stockholders' equity	4,514,473	4,234,188
Non-controlling interests	11,067	7,131
Total equity	4,525,540	4,241,319
Total liabilities and equity	6,312,024	5,793,245
Exchangeable Shares [Member]
Equity:
Common stock, value	0
Series F Preferred Stock [Member]
Equity:
Preferred Stock, value	0
Series G Preferred Stock [Member]
Equity:
Preferred Stock, value	$ 0