Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Cash	$ 667,863,000	$ 396,619,000	$ 425,316,000	$ 545,419,000
Contract land deposit impairments (recoveries), net	(1,238,000)	4,269,000	11,058,000
Contract land deposit assets impairment valuation allowances	29,999,000	31,306,000
Excess tax benefits from equity-based compensation	$ 58,681,000	0	0
Adjustment to additional paid in capital, income tax effect from share-based compensation, net		13,661,000	23,311,000
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax		609,000
Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax		(957,000)
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Operating activities		13,661,000	23,311,000
Financing activities		13,661,000	$ 23,311,000
Accounting Standards Update 2016-09 | Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative-effect adjustment from adoption of ASU 2016-09, net of tax		(957,000)
Model home furniture and fixtures
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	2 years
Office facilities and other | Minimum
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Office facilities and other | Maximum
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	10 years
Manufacturing Facilities | Minimum
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Manufacturing Facilities | Maximum
Significant Accounting Policies [Line Items]
Property, Plant and Equipment, Useful Life	40 years
Homebuilding:
Significant Accounting Policies [Line Items]
Cash	$ 645,087,000	375,748,000
Impairment of goodwill	0
Homebuilding: | Heartland Homes Inc
Significant Accounting Policies [Line Items]
Finite-lived intangibles acquired from business acquisition, net of accumulated amortization	$ 776,000	2,158,000
Weighted average life of finite-lived intangible assets	5 years
Goodwill acquired from business acquisition	$ 441,000	441,000
Mortgage Banking:
Significant Accounting Policies [Line Items]
Cash	$ 21,707,000	19,657,000
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring
Significant Accounting Policies [Line Items]
Typical length of days loans sold into secondary market	30 days
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring | Rate lock commitments
Significant Accounting Policies [Line Items]
Notional or Principal Amount	$ 490,184,000
Mortgage Banking: | Level 2 | Fair Value, Measurements, Recurring | Forward sales contracts
Significant Accounting Policies [Line Items]
Notional or Principal Amount	705,405,000
Consolidated Joint Venture
Significant Accounting Policies [Line Items]
Cash	$ 1,069,000	$ 1,214,000