Inventory (Summary of Interests in Land Option Agreements) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	$ 238,339	$ 218,568
Remaining Purchase Price	2,635,117	2,602,410
Land options with VIEs
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	99,742	90,717
Remaining Purchase Price	1,073,520	1,079,507
Other land options
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	138,597	127,851
Remaining Purchase Price	$ 1,561,597	$ 1,522,903