Unearned Revenue - Schedule of Unearned Revenue (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Jan. 01, 2018
Deferred Revenue Arrangement [Line Items]
Unearned revenue	$ 3,416,340	$ 3,448,581	$ 3,583,849
California [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	397,338	382,028	406,054
Northwest [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	383,855	362,225	315,582
Heavy Civil [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	2,076,110	2,287,770	2,399,785
Kenny [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	371,858	416,558	462,428
Water and Mineral Services [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	187,179
Construction Segment [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	1,104,457	880,976	825,428
Construction Segment [Member] | California [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	364,305	333,866	365,771
Construction Segment [Member] | Northwest [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	383,855	362,225	262,117
Construction Segment [Member] | Heavy Civil [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	43,959	54,596	43,016
Construction Segment [Member] | Kenny [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	125,159	130,289	154,524
Construction Segment [Member] | Water and Mineral Services [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	187,179
Large Project Construction [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	2,311,883	2,567,605	2,758,421
Large Project Construction [Member] | California [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	33,033	48,162	40,283
Large Project Construction [Member] | Northwest [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	0	0	53,465
Large Project Construction [Member] | Heavy Civil [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	2,032,151	2,233,174	2,356,769
Large Project Construction [Member] | Kenny [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	246,699	$ 286,269	$ 307,904
Large Project Construction [Member] | Water and Mineral Services [Member]
Deferred Revenue Arrangement [Line Items]
Unearned revenue	$ 0