Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Accrual Adjustments

	2018		2017		2016
	Millions
Compensation Cost included in Operation and Maintenance Expense	$	30	$	31	$	29
Income Tax Benefit Recognized in Consolidated Statement of Operations	$	9	$	13	$	12

Stock Options Activity

Changes in stock options for 2018 are summarized as follows:

	Options	Weighted Average Exercise Price		Weighted Average Remaining Years Contractual Term	Aggregate Intrinsic Value
Outstanding as of January 1, 2018	347,900	$	33.49
Exercised	115,967	$	33.49
Canceled/Forfeited	—	$	—
Outstanding as of December 31, 2018	231,933	$	33.49	1.0	$	4,304,676
Exercisable at December 31, 2018	231,933	$	33.49	1.0	$	4,304,676

Activity For Options Exercised

Activity for options exercised for the years ended December 31, 2018, 2017 and 2016 is shown below:

	2018		2017		2016
	Millions
Total Intrinsic Value of Options Exercised	$	2	$	5	$	7
Cash Received from Options Exercised	$	4	$	26	$	22
Tax Benefit Realized from Options Exercised	$	—	$	—	$	1

Restricted Stock Units Activity

Changes in restricted stock units for the year ended December 31, 2018 are summarized as follows:

	Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Years Contractual Term	Aggregate Intrinsic Value
Non-vested as of January 1, 2018	213,899	$	42.32
Granted	277,261	$	49.34
Vested	220,105	$	46.02
Canceled/Forfeited	13,472	$	44.94
Non-vested as of December 31, 2018	257,583	$	46.58	1.2	$	13,407,195

Performance Units Information

Changes in performance share units for the year ended December 31, 2018 are summarized as follows:

	Shares	Weighted Average Grant Date Fair Value		Weighted Average Remaining Years Contractual Term	Aggregate Intrinsic Value
Non-vested as of January 1, 2018	332,461	$	45.29
Granted	378,800	$	54.95
Vested	310,425	$	49.63
Canceled/Forfeited	23,295	$	48.57
Non-vested as of December 31, 2018	377,541	$	51.94	1.7	$	19,651,009