Share-based Compensation (Inputs Used for Valuation of Option Grants under Stock Option Plans) (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Expected volatility	35.70%	40.20%
Weighted-average volatility	35.70%	40.20%
Expected dividends	2.11%	2.89%
Risk-free rate	2.20%	1.60%
Average risk-free rate	2.20%	1.60%
Expected term (in years)	7 years 4 months 24 days	7 years 4 months 24 days
Pre-vesting departure rate	0.60%	0.60%
Minimum [Member]
Expected volatility			35.70%	40.20%
Weighted-average volatility			35.70%	40.20%
Expected dividends			2.11%	2.89%
Risk-free rate			2.20%	1.50%
Average risk-free rate			2.20%	1.50%
Expected term (in years)			7 years 4 months 24 days	7 years 4 months 24 days
Pre-vesting departure rate			0.60%	0.60%
Maximum [Member]
Expected volatility			36.10%	43.10%
Weighted-average volatility			36.10%	43.10%
Expected dividends			2.28%	2.94%
Risk-free rate			2.30%	1.60%
Average risk-free rate			2.30%	1.60%
Expected term (in years)			7 years 4 months 24 days	7 years 4 months 24 days
Pre-vesting departure rate			0.60%	0.60%