Investments in Affiliates - Investments in Affiliates (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Investments in affiliates		$ 38,469	$ 35,668	$ 33,182
Joint Venture Unconsolidated [Member]
Investment [Line Items]
Investments in affiliates		38,469	35,668
Equity Method investments in Real Estate Affiliates [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Investments in affiliates		29,472	25,911
Other Affiliates [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Investments in affiliates		8,997	9,757
Current Assets		31,320	30,836
Noncurrent Assets		129,039	124,670
Total assets		160,359	155,506
Current Liabilities		30,131	18,485
Long-Term Liabilities	[1]	31,636	37,217
Total Liabilities		61,767	55,702
Net assets		98,592	99,804
Granite’s share of net assets		38,469	35,668
Variable Interest Entity, Not Primary Beneficiary [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Total assets		28,100
Texas [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Residential Real Estate [Member] | Real Estate Entities [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Granite’s share of net assets		24,300	$ 20,800
Minimum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Total assets		1,600
Maximum [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Real Estate Entities [Member] | Joint Venture Unconsolidated [Member]
Investment [Line Items]
Total assets		$ 68,500

[1] The balance primarily relates to debt associated with our real estate investments. See Note 11 for further discussion.