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, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Investments [Line Items]
Current assets	$ 331,630	$ 226,392
Noncurrent assets	935,790	181,343
Total assets	1,267,420	407,735
Current liabilities	106,966	74,242
Noncurrent liabilities	339,604	63,585
Total liabilities	446,570	137,827
Net sales	560,376	499,394	$ 499,941
Gross profit	253,569	164,063	168,898
Income before income taxes	157,501	101,983	101,680
Net income	$ 111,491	$ 71,466	$ 71,322