Stockholders' Equity (Schedule of Stock Issued to Board of Directors) (Details) - 2014 Independent Director Equity Plan shares in Millions	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Range One
Share-based Goods and Nonemployee Services Transaction [Line Items]
Stock Units Granted (in shares) | shares	9,435
Price of Stock Units Granted (in dollars per share) | $ / shares	$ 79.51
Range Two
Share-based Goods and Nonemployee Services Transaction [Line Items]
Stock Units Granted (in shares) | shares	19,230
Price of Stock Units Granted (in dollars per share) | $ / shares	$ 39.00
Range Three
Share-based Goods and Nonemployee Services Transaction [Line Items]
Stock Units Granted (in shares) | shares	4,416
Price of Stock Units Granted (in dollars per share) | $ / shares	$ 47.03
Range Four
Share-based Goods and Nonemployee Services Transaction [Line Items]
Stock Units Granted (in shares) | shares	21,390
Price of Stock Units Granted (in dollars per share) | $ / shares	$ 42.08