Statements of Consolidated Common Stockholders' Equity (Shares) (Parenthetical) shares in Thousands	6 Months Ended
	Jun. 30, 2017 shares
Balance as of January 1, 2017	323,160
Treasury Stock acquired	(237)
Issued:
Employee stock purchase plan	103
Long-term incentive plan	221
401(k) and profit sharing	996
Dividend reinvestment plan	196
ATM Program	1,318
Balance as of June 30, 2017	325,757
Common Stock
Balance as of January 1, 2017	326,664
Issued:
Employee stock purchase plan	103
Long-term incentive plan	221
401(k) and profit sharing	996
Dividend reinvestment plan	196
ATM Program	1,318
Balance as of June 30, 2017	329,498
Treasury Stock
Balance as of January 1, 2017	(3,504)
Treasury Stock acquired	(237)
Issued:
Employee stock purchase plan	0
Long-term incentive plan	0
401(k) and profit sharing	0
Dividend reinvestment plan	0
ATM Program	0
Balance as of June 30, 2017	(3,741)