Fair Value Measurements - Amortized Cost and Estimated Fair Value of Available-for-Sale Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Measurements Of Financial Instruments [Line Items]
Debt securities	$ 13,835	$ 5,818
Total available-for-sale marketable securities	634,441	551,938
Amortized Cost [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Total available-for-sale marketable securities	632,995	547,100
Amortized Cost [Member] | Homebuilding [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Equity security	368,037	208,279
Debt securities	241,074	306,793
Total available-for-sale marketable securities	609,111	515,072
Amortized Cost [Member] | Financial Services [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Total available-for-sale marketable securities	23,884	32,028
Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Total available-for-sale marketable securities	634,441	551,938
Fair Value [Member] | Homebuilding [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Equity security	368,579	208,818
Debt securities	241,825	310,647
Total available-for-sale marketable securities	610,404	519,465
Fair Value [Member] | Financial Services [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Total available-for-sale marketable securities	$ 24,037	$ 32,473