Common Stock - Fair Value Assumptions of Stock Options Under The Black-Scholes Option-Pricing Model (Details)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Weighted-average Fair Value Assumptions [Abstract]
Expected term	5 years	4 years 10 months 24 days	4 years 9 months 18 days
Expected volatility	31.86%	32.92%	30.68%
Risk-free interest rate	0.98%	0.80%	2.17%
Dividend yield	1.13%	1.11%	1.13%