Stockholders' Equity and Equity Instruments - Fair Value, Exercise Price Range, and Accumulated Other Comprehensive Income (Details) - Stock Options [Member]	9 Months Ended
	Sep. 30, 2015 $ / shares
Fair value assumptions and methodology [Abstract]
Lower limit of fair value of options granted (in dollars per share)	$ 14.22
Upper limit of fair value of options granted (in dollars per share)	$ 15.09
Lower limit of expected volatility (in hundredths)	24.70%
Upper limit of expected volatility (in hundredths)	25.00%
Dividend yield (in hundredths)	3.10%
Risk-free rate of return lower limit (in hundredths)	1.30%
Risk-free rate of return upper limit (in hundredths)	1.60%
Minimum [Member]
Fair value assumptions and methodology [Abstract]
Exercise price (in dollars per share)	$ 91.75
Expected term	4 years 6 months
Maximum [Member]
Fair value assumptions and methodology [Abstract]
Exercise price (in dollars per share)	$ 93.26
Expected term	5 years