Summary of Significant Accounting Policies (Calculations of Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Net income (loss) attributable to Tutor Perini Corporation	$ 35,495	$ 36,819	$ 18,709	$ 17,371	$ (86,117)	$ 19,313	$ (320,530)	$ (356)	$ 108,394	$ (387,690)	$ 83,436
Weighted-average common shares outstanding, basic (in shares)									50,656	50,220	49,952
Effect of dilutive restricted stock units and stock options (in shares)									421	0	349
Weighted-average common shares outstanding, diluted (in shares)									51,077	50,220	50,301
Basic (in dollars per share)	$ 0.70	$ 0.72	$ 0.37	$ 0.35	$ (1.71)	$ 0.38	$ (6.38)	$ (0.01)	$ 2.14	$ (7.72)	$ 1.67
Diluted (in dollars per share)	$ 0.69	$ 0.72	$ 0.37	$ 0.34	$ (1.71)	$ 0.38	$ (6.38)	$ (0.01)	$ 2.12	$ (7.72)	$ 1.66
Anti-dilutive securities not included above (in shares)									1,862	3,640	2,670