Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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

Accrual Adjustments

	2016		2015		2014
	Millions
Compensation Cost included in Operation and Maintenance Expense	$	29	$	34	$	32
Income Tax Benefit Recognized in Consolidated Statement of Operations	$	12	$	14	$	13

Stock Options Activity

Changes in stock options for 2016 are summarized as follows:

	Options	Weighted Average Exercise Price		Weighted Average Remaining Years Contractual Term	Aggregate Intrinsic Value
Outstanding as of January 1, 2016	1,707,250	$	36.00
Exercised	677,350	$	33.06
Canceled/Forfeited	—	$	—
Outstanding as of December 31, 2016	1,029,900	$	37.93	2.0	$	7,640,178
Exercisable at December 31, 2016	1,029,900	$	37.93	2.0	$	7,640,178

Activity For Options Exercised

Activity for options exercised for the years ended December 31, 2016, 2015 and 2014 is shown below:

	2016		2015		2014
	Millions
Total Intrinsic Value of Options Exercised	$	7	$	3	$	4
Cash Received from Options Exercised	$	22	$	12	$	16
Tax Benefit Realized from Options Exercised	$	1	$	—	$	—

Restricted Stock Units Activity

Changes in restricted stock units for the year ended December 31, 2016 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, 2016	408,507	$	34.95
Granted	285,258	$	42.28
Vested	362,098	$	37.23
Canceled/Forfeited	9,471	$	39.67
Non-vested as of December 31, 2016	322,196	$	38.75	1.0	$	14,137,960

Performance Units Information

Changes in performance share units for the year ended December 31, 2016 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, 2016	403,961	$	40.42
Granted	319,718	$	45.97
Vested	301,554	$	41.22
Canceled/Forfeited	28,313	$	42.04
Non-vested as of December 31, 2016	393,812	$	44.20	1.6	$	17,280,471