Investments Summary of Assets, Liabilities and Results of Operations for Significant Unconsolidated Joint Ventures (Details) - Significant Unconsolidated Joint Ventures - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Investments [Line Items]
Current assets	$ 383,203	$ 331,630
Noncurrent assets	913,643	935,790
Total assets	1,296,846	1,267,420
Current liabilities	138,474	106,966
Noncurrent liabilities	319,801	339,604
Total liabilities	458,275	446,570
Net sales	590,980	560,376	$ 499,394
Gross profit	267,241	253,569	164,063
Income before income taxes	189,016	157,501	101,983
Net income	$ 126,872	$ 111,491	$ 71,466