Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Other Long-Term Liabilities [Line Items]
Supplemental employees' retirement plan (SERP)	$ 158,984	$ 141,546
Total	51,427	45,647
Other Liabilties [Member]
Other Long-Term Liabilities [Line Items]
Supplemental employees' retirement plan (SERP)	9,654	9,818
Deferred compensation	16,244	14,601
Long-term incentive plan	7,973	7,527
Noncurrent income taxes payable	2,672	2,300
Environmental remediation liability	9,307	7,370
Other	5,577	4,031
Total	$ 51,427	$ 45,647