Stockholders' Equity - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Shares
Beginning balance, outstanding (in shares)	405,000
Granted (in shares)	0	0
Exercised (in shares)	0
Ending balance, outstanding (in shares)	405,000	405,000
Weighted Average Exercise Price
Beginning balance, outstanding (usd per share)	$ 64.79
Granted (usd per share)	0
Exercised (usd per share)	0
Ending balance, outstanding (usd per share)	$ 64.79	$ 64.79
Outstanding, Aggregate Intrinsic Value	$ 29
Outstanding, Weighted Average Remaining Contractual term	7 years 4 months 24 days
Stock options exercisable and expected to vest (in shares)	405,000
Stock options exercisable and expected to vest (usd per share)	$ 64.79
Exercisable (in shares)	280,000
Exercisable (usd per share)	$ 63.65
Exercisable, Aggregate Intrinsic Value	$ 20
Exercisable, Weighted Average Remaining Contractual term	7 years 3 months 18 days

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.