Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 25
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=51819886&loc=SL6014347-161799

Debt - Narrative (Detail)		3 Months Ended		6 Months Ended
Debt - Narrative (Detail)	May 15, 2020 USD ($) day $ / shares shares	Jun. 30, 2020 USD ($) $ / shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) day $ / shares	Jun. 30, 2019 USD ($)	May 19, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Increased inventory under credit facilities		$ 135,400,000		$ 135,400,000			$ 836,600,000
Increased borrowings under credit facilities		117,200,000		117,200,000			691,500,000
Gain on partial extinguishment		6,391,000	$ 0	6,391,000	$ 0
Class C Capital Stock
Debt Instrument [Line Items]
Shares received in unwinding of capped call transactions \| shares	317,865
Value based on trading price of Class C capital stock at time of unwind	$ 14,800,000
Convertible Debt
Debt Instrument [Line Items]
Aggregate Principal Amount		2,386,717,000		2,386,717,000
Unamortized Debt Discount and Debt Issuance Costs		566,739,000		$ 566,739,000			463,348,000
2024 and 2026 Notes \| Convertible Debt
Debt Instrument [Line Items]
Debt instrument, threshold consecutive trading days \| day				30
Debt Instrument, convertible threshold percentage				130.00%
2.75% convertible senior notes due 2025 \| Convertible Debt
Debt Instrument [Line Items]
Debt instrument, convertible threshold trading days \| day	20
Debt instrument, threshold consecutive trading days \| day	30
Debt Instrument, convertible threshold percentage	130.00%
Aggregate Principal Amount	$ 500,000,000.0	$ 565,000,000		$ 565,000,000		$ 65,000,000.0
Stated Interest Rate	2.75%	2.75%		2.75%		2.75%
Net proceeds from issuance	$ 553,300,000
Remaining consideration allocated to equity component	$ 154,800,000
Conversion Price per Share (usd per share) \| $ / shares	$ 67.20	$ 67.20		$ 67.20
Unamortized Debt Discount and Debt Issuance Costs	$ 3,300,000	$ 163,214,000		$ 163,214,000			0
2.75% convertible senior notes due 2025 \| Convertible Debt \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Repurchase price percentage of principal amount	100.00%
2.75% convertible senior notes due 2025 \| Convertible Debt \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Repurchase price percentage of principal amount	100.00%
2.00% convertible senior notes due 2021 \| Convertible Debt
Debt Instrument [Line Items]
Aggregate Principal Amount		$ 265,330,000		$ 265,330,000
Stated Interest Rate		2.00%		2.00%
Repurchased amount	$ 194,700,000
Cash paid for repurchase	194,700,000
Aggregate purchase price	230,900,000
Fair value of liability component	172,900,000
Remaining consideration allocated to equity component	58,000,000.0
Reduction to long-term debt	179,300,000
Reduction to additional paid-in capital	58,000,000.0
Gain on partial extinguishment	$ 6,400,000
Conversion Price per Share (usd per share) \| $ / shares		$ 52.36		$ 52.36
Unamortized Debt Discount and Debt Issuance Costs		$ 19,333,000		$ 19,333,000			44,498,000
2.00% convertible senior notes due 2021 \| Convertible Debt \| Class C Capital Stock
Debt Instrument [Line Items]
Shares issued in debt conversion \| shares	753,936
Citibank, N.A.
Debt Instrument [Line Items]
Repurchase agreement, committed amount		25,000,000.0		25,000,000.0
Citibank, N.A. \| Mortgages Segment
Debt Instrument [Line Items]
Short-term debt		$ 33,918,000		$ 33,918,000			$ 394,000