Acquisitions and Equity Investments - Additional Information (Detail)		1 Months Ended	12 Months Ended
	Oct. 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Dec. 31, 2019 USD ($) Segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of reportable segments | Segment			3
Number of operating segments | Segment			3
Non-cash impairment charge			$ 0	$ 79,000,000	$ 174,000,000
June 2017 Investment
Schedule of Equity Method Investments [Line Items]
Equity interest in privately held corporation				0.0		$ 10,000,000.0
Non-cash impairment charge				$ 10,000,000.0
October 2016 Investment
Schedule of Equity Method Investments [Line Items]
Cumulative impairment charge			0
Upward adjustments			0
Downward adjustments			0
October 2016 Investment | Variable Interest Entity, Not Primary Beneficiary
Schedule of Equity Method Investments [Line Items]
Equity interest in privately held corporation		$ 10,000,000.0
Percentage of equity interest in privately held variable interest entity		10.00%
Maximum exposure to loss in variable interest entity			$ 10,000,000.0
Mortgage Lenders of America, L.L.C.
Schedule of Equity Method Investments [Line Items]
Business acquisition, purchase price	$ 66,700,000
Unaudited pro forma revenue				3.00%	5.00%