Consolidated Balance Sheets - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 166.3	$ 170.6
Accounts receivable, net	232.9	191.0
Materials and supplies	155.4	152.6
Other current assets	156.8	133.8
Total current assets	711.4	648.0
Investments	36.2	32.9
Property and equipment (including concession assets), net	8,247.3	8,069.7
Other assets	72.7	66.9
Total assets	9,067.6	8,817.5
Current liabilities:
Long-term debt due within one year	42.2	25.4
Short-term borrowings	302.8	181.3
Accounts payable and accrued liabilities	476.3	537.7
Total current liabilities	821.3	744.4
Long-term debt	2,243.6	2,271.5
Deferred income taxes	1,385.4	1,289.3
Other noncurrent liabilities and deferred credits	109.5	107.8
Total liabilities	4,559.8	4,413.0
Stockholders' equity:
$.01 par, common stock, 400,000,000 shares authorized; 123,352,185 shares issued; 105,382,492 and 106,606,619 shares outstanding at June 30, 2017 and December 31, 2016, respectively	1.1	1.1
Additional paid-in capital	954.6	954.8
Retained earnings	3,238.0	3,134.1
Accumulated other comprehensive loss	(7.2)	(6.2)
Total stockholders’ equity	4,192.6	4,089.9
Noncontrolling interest	315.2	314.6
Total equity	4,507.8	4,404.5
Total liabilities and equity	9,067.6	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