Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 88.4	$ 170.6
Accounts receivable, net	237.2	191.0
Materials and supplies	151.2	152.6
Other current assets	163.7	133.8
Total current assets	640.5	648.0
Investments	51.9	32.9
Property and equipment (including concession assets), net	8,335.6	8,069.7
Other assets	72.3	66.9
Total assets	9,100.3	8,817.5
Current liabilities:
Long-term debt due within one year	40.5	25.4
Short-term borrowings	355.9	181.3
Accounts payable and accrued liabilities	528.4	537.7
Total current liabilities	924.8	744.4
Long-term debt	2,238.4	2,271.5
Deferred income taxes	1,432.3	1,289.3
Other noncurrent liabilities and deferred credits	98.4	107.8
Total liabilities	4,693.9	4,413.0
Stockholders' equity:
$.01 par, common stock, 400,000,000 shares authorized; 123,352,185 shares issued; 103,694,613 and 106,606,619 shares outstanding at September 30, 2017 and December 31, 2016, respectively	1.0	1.1
Additional paid-in capital	930.5	954.8
Retained earnings	3,160.9	3,134.1
Accumulated other comprehensive loss	(7.9)	(6.2)
Total stockholders’ equity	4,090.6	4,089.9
Noncontrolling interest	315.8	314.6
Total equity	4,406.4	4,404.5
Total liabilities and equity	9,100.3	8,817.5
$25 Par Preferred Stock [Member]
Stockholders' equity:
$25 par, 4% noncumulative, preferred stock, 840,000 shares authorized, 649,736 shares issued, 242,170 shares outstanding	$ 6.1	$ 6.1