Construction and Line Item Joint Ventures - Consolidated Construction Joint Ventures (Details) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Construction Joint Venture [Line Items]
Cash and cash equivalents		$ 221,785	$ 167,174	$ 221,785	$ 167,174	$ 255,961	$ 229,121
Other current assets		18,863	21,743	18,863	21,743	23,033
Total current assets		1,102,736	1,020,829	1,102,736	1,020,829	970,178
Property and equipment, net		385,036	424,272	385,036	424,272	409,653
Other noncurrent assets		73,412	75,826	73,412	75,826	77,940
Total assets		1,718,706	1,683,043	1,718,706	1,683,043	1,620,494
Accounts payable		196,885	205,493	196,885	205,493	151,935
Billings in excess of costs and estimated earnings		122,409	115,809	122,409	115,809	108,992
Accrued expenses and other current liabilities		224,101	221,618	224,101	221,618	200,652
Total current liabilities		549,239	544,167	549,239	544,167	462,826
Construction		427,018	447,097	921,143	873,357
Net cash used in operating activities				(8,129)	(46,833)
Granite Construction [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Unconsolidated Construction Joint Venture Net Income		11,100	1,800	29,700	28,100
Partnership Interest [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures		5,600,000		5,600,000
Joint Venture Consolidated [Member] | Consolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Cash and cash equivalents	[1]	41,052	29,518	41,052	29,518	61,276
Receivables, Net		36,527	45,483	36,527	45,483	36,781
Cost and estimated earnings in excess of billings	[1]	365	21,105	365	21,105	129
Other current assets		2,020	1,910	2,020	1,910	1,617
Total current assets		79,964	98,016	79,964	98,016	99,803
Property and equipment, net		6,068	16,172	6,068	16,172	11,969
Total assets	[2]	86,032	114,188	86,032	114,188	111,772
Accounts payable		10,438	22,951	10,438	22,951	18,009
Billings in excess of costs and estimated earnings	[1]	13,794	23,138	13,794	23,138	32,830
Accrued expenses and other current liabilities		1,148	3,110	1,148	3,110	2,714
Total liabilities	[2]	$ 25,380	49,199	$ 25,380	49,199	$ 53,553
Number of Active Joint Venture Projects		3		3
Joint Venture Unconsolidated [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Unconsolidated Construction Joint Venture Net Income		$ 19,500	25,200	$ 86,900	75,200
Number of Active Joint Venture Projects		11		11
Joint Venture Unconsolidated [Member] | Line Item Joint Venture [Member]
Construction Joint Venture [Line Items]
Number of Active Joint Venture Projects		5		5
Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures		$ 1,700,000		$ 1,700,000
Other Partners Interest in Partnerships [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures		3,900,000		3,900,000
Minimum [Member] | Joint Venture Consolidated [Member] | Consolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		600		600
Revenue Remaining to be Recognized on Consolidated Construction Joint Ventures		$ 200		$ 200
Proportionate Share of the Consolidated Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly		50.00%		50.00%
Construction		$ 14,000	$ 23,800	$ 39,000	122,000
Net cash used in operating activities				16,800	$ 44,700
Minimum [Member] | Joint Venture Unconsolidated [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		$ 73,600		$ 73,600
Proportionate Share of the Consolidated Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly		20.00%		20.00%
Minimum [Member] | Joint Venture Unconsolidated [Member] | Line Item Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		$ 42,400		$ 42,400
Revenue Per Project Remaining to be Recognized on Line Item Construction Joint Ventures		1,300		1,300
Minimum [Member] | Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures		3,200		3,200
Minimum [Member] | Reporting Entitys Interest in Joint Venture [Member] | Line Item Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		28,500		28,500
Maximum [Member] | Joint Venture Consolidated [Member] | Consolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		293,800		293,800
Revenue Remaining to be Recognized on Consolidated Construction Joint Ventures		$ 119,700		$ 119,700
Proportionate Share of the Consolidated Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly		65.00%		65.00%
Maximum [Member] | Joint Venture Unconsolidated [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		$ 3,400,000		$ 3,400,000
Proportionate Share of the Consolidated Joint Ventures Equity Owned by or Beneficial Interest in the Reporting Entity Directly or Indirectly		50.00%		50.00%
Maximum [Member] | Joint Venture Unconsolidated [Member] | Line Item Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		$ 87,100		$ 87,100
Revenue Per Project Remaining to be Recognized on Line Item Construction Joint Ventures		39,800		39,800
Maximum [Member] | Reporting Entitys Interest in Joint Venture [Member] | Unconsolidated Construction Joint Venture [Member]
Construction Joint Venture [Line Items]
Revenue Remaining to be Recognized on Unconsolidated Construction Joint Ventures		632,200		632,200
Maximum [Member] | Reporting Entitys Interest in Joint Venture [Member] | Line Item Joint Venture [Member]
Construction Joint Venture [Line Items]
Construction Contract Value		$ 64,600		$ 64,600

[1] The volume and stage of completion of contracts from our consolidated construction joint ventures may cause fluctuations in cash and cash equivalents as well as billings in excess of costs and estimated earnings and costs in excess of billings and estimated earnings between periods.

[2] The assets and liabilities of each consolidated joint venture relate solely to that joint venture. The decision to distribute joint venture cash and cash equivalents and assets must generally be made jointly by a majority of the members and, accordingly, these cash and cash equivalents and assets generally are not available for the working capital needs of Granite until distributed.