Summary of Significant Accounting Policies (Tax Effects of Components of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Defined benefit pension plan adjustments, Before-Tax Amount	$ (8,700)	$ 1,180	$ 1,079
Defined benefit pension plan adjustments, Tax (Expense) Benefit	2,439	(336)	(308)
Defined benefit pension plan adjustments, Net-of-Tax Amount	(6,261)	844	771
Foreign currency translation adjustment, Before-Tax Amount	178	1,867	(4,067)
Foreign currency translation adjustment, Tax (Expense) Benefit	101	(530)	1,122
Foreign currency translation adjustment, Net-of-Tax Amount	279	1,337	(2,945)
Unrealized gain (loss) in fair value of investments, Before-Tax Amount	2,015	1,982	(1,005)
Unrealized gain (loss) in fair value of investments, Tax (Expense) Benefit	(444)	(421)	227
Unrealized gain (loss) in fair value of investments, Net-of-Tax Amount	1,571	1,561	(778)
Total other comprehensive income (loss), Before-Tax Amount	(6,507)	5,029	(3,993)
Total other comprehensive income (loss), Tax (Expense) Benefit	2,096	(1,287)	1,041
Total other comprehensive income (loss), Net-of-Tax Amount	(4,411)	3,742	(2,952)
Less: Other comprehensive income (loss) attributable to noncontrolling interests, Before-Tax Amount	230	393	(221)
Less: Other comprehensive income (loss) attributable to noncontrolling interest, Tax (Expense) Benefit	0	0	0
Less: Other comprehensive income (loss) attributable to noncontrolling interests, Net-of-Tax Amount	230	393	(221)
Total other comprehensive income (loss) attributable to Tutor Perini Corporation, Before-Tax Amount	(6,737)	4,636	(3,772)
Total other comprehensive income (loss) attributable to Tutor Perini Corporation, Tax (Expense) Benefit	2,096	(1,287)	1,041
Total other comprehensive income (loss) attributable to Tutor Perini Corporation, Net-of-Tax Amount	$ (4,641)	$ 3,349	$ (2,731)