Stock Option Black Scholes Option Pricing Model Assumptions (Details) - Employee Stock Option [Member] - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Expected volatility	32.70%	33.50%
Risk-free interest rate	2.00%	1.30%
Expected term (years)	5 years 6 months	5 years 6 months
Granted, Weighted Average Grant Date Fair Value	$ 22.01	$ 13.15