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Stockholders' Equity (Summary of Assumptions Used to Value Stock Option Grants) (Details)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2019
USD ($)
$ / shares
Dec. 31, 2018
USD ($)
$ / shares
Dec. 31, 2017
USD ($)
$ / shares
Stockholders' Equity Note [Abstract]      
Dividend yield 0.00% 0.00% 0.00%
Expected volatility, minimum 37.00% 40.00% 34.00%
Expected volatility, maximum 41.00% 42.00% 37.00%
Risk-free interest rate, minimum 1.74% 2.61% 2.24%
Risk-free interest rate, maximum 2.74% 3.09% 2.45%
Suboptimal exercise factor, minimum 3.07 2.80 2.48
Suboptimal exercise factor, maximum 3.23 3.01 2.63
Valuation data:      
Weighted-average fair value (in USD per share) | $ / shares $ 156.60 $ 157.19 $ 71.45
Total stock-based compensation expense $ 405,376 $ 320,657 $ 182,209
Total income tax impact on provision $ 90,856 $ 67,575 $ 61,842