Inventory (Summary of Interests in Land Option Agreements) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	$ 287,557	$ 218,568
Remaining Purchase Price	3,255,948	2,602,410
Land options with VIEs
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	120,490	90,717
Remaining Purchase Price	1,238,526	1,079,507
Other land options
Variable Interest Entity [Line Items]
Deposits and Pre-acquisition Costs	167,067	127,851
Remaining Purchase Price	$ 2,017,422	$ 1,522,903