Stockholders' Equity (Narrative) (Details)	Mar. 31, 2020 USD ($) shares	Dec. 31, 2019 shares	Nov. 27, 2019 £ / shares shares	Dec. 11, 2018 USD ($)	Apr. 25, 2017 USD ($)
Stockholders' Equity Note [Abstract]
Canceled shares (in shares) | shares		4,000,000	50,000
Shares Issued, Price Per Share | £ / shares			£ 1
Stock repurchase program, authorized amount | $	$ 800,000,000.0			$ 300,000,000.0	$ 500,000,000.0