Fair Value Measurement (Schedule Of Available-For-Sale Securities Investments Results)(Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities, amoritzed cost	$ 8,040,000	$ 8,260,000
Available-for-sales securities, gross unrealized gains	16,270,000	16,500,000
Available-for-sale securities, gross unrealized losses	0	0
Avaialbe-for-sale securities gross, Fair Value	24,310,000	24,760,000
Deferred taxes on unrealized holdings gains	6,508,000	6,600,000
Unrealized gains recorded in equity, net of deferred tax	9,762,000	9,900,000
Cement Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities, amoritzed cost	3,790,000	4,190,000
Available-for-sales securities, gross unrealized gains	9,240,000	8,290,000
Available-for-sale securities, gross unrealized losses	0	0
Avaialbe-for-sale securities gross, Fair Value	13,030,000	12,480,000
General Buiding Materials Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities, amoritzed cost	3,600,000	3,600,000
Available-for-sales securities, gross unrealized gains	2,110,000	2,150,000
Available-for-sale securities, gross unrealized losses	0	0
Avaialbe-for-sale securities gross, Fair Value	5,710,000	5,750,000
Oil And Gas Refining And Marketing Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities, amoritzed cost	340,000	470,000
Available-for-sales securities, gross unrealized gains	4,920,000	6,060,000
Available-for-sale securities, gross unrealized losses	0	0
Avaialbe-for-sale securities gross, Fair Value	5,260,000	6,530,000
Residential Construction Industry [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale equity securities, amoritzed cost	310,000
Available-for-sales securities, gross unrealized gains	0
Available-for-sale securities, gross unrealized losses	0
Avaialbe-for-sale securities gross, Fair Value	$ 310,000