Interim Financial Data - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Sep. 30, 2019	Apr. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Restructuring and related activities, description	On April 16, 2019, we announced that we will restructure our field operations over the next two years to better serve our dealer partners by streamlining our field office structure into three regional locations and investing in new technology. Costs associated with this restructure are not expected to be significant.
Operating lease right-of-use assets	$ 112
Operating lease liabilities	119
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets	76	$ 115
Operating lease liabilities	$ 76	$ 122