Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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 the status of non-vested awards as of December 31, 2015 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, 2015	480,933		(a)	$	51.27	324,230		$	54.92
Granted	152,651			64.12		151,430		64.97
Change in performance factor	—			—		40,496		54.98
Vested	(198,424	)		49.20		(202,480	)	54.98
Forfeited	(6,873	)		56.78		(7,844	)	57.89
Nonvested at December 31, 2015	428,287			56.69		305,832		59.78
Vested Awards Outstanding at December 31, 2015	106,712					202,480

(a) Includes 127,634 of awards that will be cash settled and 353,299 of awards that will be settled in shares.

(b) Nonvested performance shares are reflected at target payout level.  The 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.

The following table is a summary of awards granted and the weighted-average fair value for the three years ended 2015, 2014 and 2013.

	Restricted Stock Units, Stock Grants, and Stock Units (a)						Performance Shares (b)
	2015		2014		2013		2015		2014		2013
Units granted	152,651		179,291		182,240		151,430		166,244		176,332
Weighted-average grant date fair value	$	64.12	$	54.89	$	55.14	$	64.97	$	54.86	$	55.45

(a) Units granted includes awards that will be cash settled of 45,104 in 2015, 49,018 in 2014, and 52,620 in 2013.

(b) Reflects the target payout level.

Summary of Nonvested Performance Shares

The following table is a summary of awards granted and the weighted-average fair value for the three years ended 2015, 2014 and 2013.

	Restricted Stock Units, Stock Grants, and Stock Units (a)						Performance Shares (b)
	2015		2014		2013		2015		2014		2013
Units granted	152,651		179,291		182,240		151,430		166,244		176,332
Weighted-average grant date fair value	$	64.12	$	54.89	$	55.14	$	64.97	$	54.86	$	55.45

(a) Units granted includes awards that will be cash settled of 45,104 in 2015, 49,018 in 2014, and 52,620 in 2013.

(b) Reflects the target payout level.

The following table is a summary of the status of non-vested awards as of December 31, 2015 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, 2015	480,933		(a)	$	51.27	324,230		$	54.92
Granted	152,651			64.12		151,430		64.97
Change in performance factor	—			—		40,496		54.98
Vested	(198,424	)		49.20		(202,480	)	54.98
Forfeited	(6,873	)		56.78		(7,844	)	57.89
Nonvested at December 31, 2015	428,287			56.69		305,832		59.78
Vested Awards Outstanding at December 31, 2015	106,712					202,480

(a) Includes 127,634 of awards that will be cash settled and 353,299 of awards that will be settled in shares.

(b) Nonvested performance shares are reflected at target payout level.  The 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.