CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 670,695	$ 438,319
Short-term investments	1,256,724	1,591,740
Trade receivables	647,332	715,292
Merchandise inventories	1,706,304	1,722,392
Prepaid expenses	48,915	50,434
Total current assets	4,329,970	4,518,177
Long-term investments	5,243,817	5,146,878
Other noncurrent assets	562,896	434,280
Property, plant and equipment	12,825,095	11,981,632
Accumulated depreciation	(4,992,734)	(4,694,509)
Net property, plant and equipment	7,832,361	7,287,123
Total assets	17,969,044	17,386,458
Current liabilities:
Accounts payable	1,778,927	1,609,652
Accrued expenses:
Contributions to retirement plans	444,509	525,668
Self-insurance reserves	142,825	139,554
Salaries and wages	253,615	127,856
Other	398,274	414,197
Current portion of long-term debt	65,417	113,999
Federal and state income taxes	162,361	12,787
Total current liabilities	3,245,928	2,943,713
Deferred tax liabilities	462,537	396,484
Self-insurance reserves	214,546	216,125
Accrued postretirement benefit cost	102,884	102,540
Long-term debt	153,186	136,585
Other noncurrent liabilities	87,428	93,574
Total liabilities	4,266,509	3,889,021
Common stock related to Employee Stock Ownership Plan (ESOP)	3,122,163	3,068,097
Stockholders’ equity:
Common stock of $1 par value. Authorized 1,000,000 shares; issued 770,415 shares in 2017 and 763,198 shares in 2016	770,415	763,198
Additional paid-in capital	3,139,647	2,849,947
Retained earnings	10,842,179	9,836,696
Treasury stock at cost; 30,247 shares in 2017	(1,158,839)	0
Accumulated other comprehensive earnings	70,657	23,427
Common stock related to ESOP	(3,122,163)	(3,068,097)
Total stockholders’ equity	10,541,896	10,405,171
Noncontrolling interests	38,476	24,169
Total equity	13,702,535	13,497,437
Total liabilities and stockholders' equity	$ 17,969,044	$ 17,386,458