Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

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

Summary of Nonvested Restricted Stock, Stock Grants and Stock Units

The following table is a summary of awards granted and the weighted-average grant date fair value for the three years ended 2016, 2015 and 2014.

	Restricted Stock Units, Stock Grants, and Stock Units (a)						Performance Shares (b)
	2016		2015		2014		2016		2015		2014
Units granted	141,811		152,651		179,291		166,666		151,430		166,244
Weighted-average grant date fair value	$	67.34	$	64.12	$	54.89	$	66.60	$	64.97	$	54.86

(a) Units granted includes awards that will be cash settled of 43,952 in 2016, 45,104 in 2015, and 49,018 in 2014.

(b) Reflects the target payout level.

The following table is a summary of the status of non-vested awards as of December 31, 2016 and changes during the year.

	Restricted Stock Units, Stock Grants, and Stock Units					Performance Shares
	Shares			Weighted-Average Grant Date Fair Value		Shares (b)		Weighted-Average Grant Date Fair Value
Nonvested at January 1, 2016	428,287			$	56.69	305,832		$	58.86
Granted	141,811			67.34		166,666		66.60
Change in performance factor	—			—		15,573		54.09
Vested	(230,881	)		55.07		(171,303	)	54.09
Forfeited (c)	(3,958	)		62.86		(4,044	)	62.34
Nonvested at December 31, 2016	335,259		(a)	62.04		312,724		65.32
Vested Awards Outstanding at December 31, 2016	174,201					171,303

(a) Includes 112,554 of awards that will be cash settled.

(b) The nonvested performance shares are reflected at target payout level.  The performance metric component increase or decrease in the number of shares from the target level to the estimated actual payout level is included in the increase for performance factor amounts in the year the award vests.

(c) We account for forfeitures as they occur.

Summary of Nonvested Performance Shares

The following table is a summary of the status of non-vested awards as of December 31, 2016 and changes during the year.

	Restricted Stock Units, Stock Grants, and Stock Units					Performance Shares
	Shares			Weighted-Average Grant Date Fair Value		Shares (b)		Weighted-Average Grant Date Fair Value
Nonvested at January 1, 2016	428,287			$	56.69	305,832		$	58.86
Granted	141,811			67.34		166,666		66.60
Change in performance factor	—			—		15,573		54.09
Vested	(230,881	)		55.07		(171,303	)	54.09
Forfeited (c)	(3,958	)		62.86		(4,044	)	62.34
Nonvested at December 31, 2016	335,259		(a)	62.04		312,724		65.32
Vested Awards Outstanding at December 31, 2016	174,201					171,303

(a) Includes 112,554 of awards that will be cash settled.

(b) The nonvested performance shares are reflected at target payout level.  The performance metric component increase or decrease in the number of shares from the target level to the estimated actual payout level is included in the increase for performance factor amounts in the year the award vests.

(c) We account for forfeitures as they occur.

The following table is a summary of awards granted and the weighted-average grant date fair value for the three years ended 2016, 2015 and 2014.

	Restricted Stock Units, Stock Grants, and Stock Units (a)						Performance Shares (b)
	2016		2015		2014		2016		2015		2014
Units granted	141,811		152,651		179,291		166,666		151,430		166,244
Weighted-average grant date fair value	$	67.34	$	64.12	$	54.89	$	66.60	$	64.97	$	54.86

(a) Units granted includes awards that will be cash settled of 43,952 in 2016, 45,104 in 2015, and 49,018 in 2014.

(b) Reflects the target payout level.