Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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

Schedule of assumptions used in estimating fair value of stock options using Black-Scholes option pricing model

In determining the estimated fair value of our stock options as of the date of grant, we used the Black-Scholes option pricing model with the following assumptions:

	2017		2016		2015
Risk-free interest rate	1.69-1.87%		0.93-1.27%		1.02 - 1.38%
Dividend yield	6.00	%	5.50	%	5.00	%
Volatility factors of the expected market price for our common stock	21.5-21.6%		19.1-20.6%		19.0 - 20.0%
Weighted average expected life of options	4.0 years		4.0 years		4.0 years

Summary of stock option activity

The following is a summary of stock option activity in 2017:

	Shares (000’s)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)	Intrinsic Value ($000’s)
Outstanding as of December 31, 2016	3,805		$	56.05
Options granted	1,626		61.93
Options exercised	(349	)	46.70
Options forfeited	(57	)	58.87
Outstanding as of December 31, 2017	5,025		58.57		7.2	$	19,522
Exercisable as of December 31, 2017	3,407		$	57.01	6.5	$	18,602

Summary of status of nonvested restricted stock and restricted stock units and changes during the year

A summary of the status of our non-vested restricted stock and restricted stock units as of December 31, 2017, and changes during the year ended December 31, 2017 follows:

	Restricted Stock (000’s)		Weighted Average Grant Date Fair Value		Restricted Stock Units (000’s)		Weighted Average Grant Date Fair Value
Nonvested at December 31, 2016	312		$	57.29	15		$	58.70
Granted	283		59.99		409		62.07
Vested	(258	)	58.82		(10	)	59.59
Forfeited	(18	)	58.95		—		—
Nonvested at December 31, 2017	319		$	58.36	414		$	62.01