Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Consolidated Statements of Operations [Abstract]
Revenues	$ 3,716,317	$ 3,199,210	$ 5,151,966
Cost of Operations	3,320,976	2,861,362	4,763,919
Gross Profit	395,341	337,848	388,047
General and Administrative Expenses	226,965	165,536	176,504
INCOME FROM CONSTRUCTION OPERATIONS	168,376	172,312	211,543
Other Income (Expense), Net	4,421	(2,280)	1,098
Interest Expense	(35,750)	(10,564)	(7,501)
Income before Income Taxes	137,047	159,468	205,140
Provision for Income Taxes	(50,899)	(55,968)	(68,079)
NET INCOME	$ 86,148	$ 103,500	$ 137,061
BASIC EARNINGS PER COMMON SHARE (in dollars per share)	$ 1.82	$ 2.15	$ 2.82
DILUTED EARNINGS PER COMMON SHARE (in dollars per share)	$ 1.80	$ 2.13	$ 2.79
WEIGHTED AVERAGE COMMON SHARES OUTSTANDING:
BASIC (in shares)	47,226	48,111	48,525
Effect of Dilutive Stock Options and Restricted Stock Units (in shares)	664	538	559
DILUTED (in shares)	47,890	48,649	49,084