Summary of Significant Accounting Policies - Percentages of companys consolidated revenues recorded under percentage-of-completion method (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Summary Of Significant Accounting Policies [Abstract]
Percentage-of-Completion Revenues	16.30%	17.30%	14.10%	16.60%