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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, 2015
USD ($)
$ / shares
Dec. 31, 2014
USD ($)
$ / shares
Dec. 31, 2013
USD ($)
$ / shares
Stockholders' Equity Note [Abstract]      
Dividend yield 0.00% 0.00% 0.00%
Expected volatility, minimum 36.00% 41.00% 51.00%
Expected volatility, maximum 53.00% 48.00% 54.00%
Risk-free interest rate, minimum 2.03% 2.39% 1.87%
Risk-free interest rate, maximum 2.29% 2.83% 2.71%
Suboptimal exercise factor, minimum 2.47 2.66 2.33
Suboptimal exercise factor, maximum 2.48 5.44 3.92
Valuation data:      
Weighted-average fair value (in USD per share) | $ / shares $ 39.22 $ 30.17 $ 16.25
Total stock-based compensation expense (in thousands) $ 124,725 $ 115,239 $ 73,100
Total income tax impact on provision (in thousands) $ 47,125 $ 43,999 $ 28,096