Description of Business and Significant Accounting Policies - Recent Accounting Pronouncements (Details) - ASC 326 - USD ($) $ in Millions		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to allowance for credit losses	$ 44
Adjustment tax rate		24.00%
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase to allowance for credit losses	$ 36