Summary of Significant Accounting Policies - The Company (Details) a in Thousands	12 Months Ended
	Dec. 31, 2018 segment joint_venture mi	Dec. 31, 2018 variable_interest_entity	Dec. 31, 2018 a	Dec. 31, 2017 variable_interest_entity
Revenues from External Customers and Long-Lived Assets [Line Items]
Business segments | segment	5
Area of land | a			270
Number of joint ventures	8	2		2
Los Angeles, California
Revenues from External Customers and Long-Lived Assets [Line Items]
Distance from city	60
Bakersfield, California
Revenues from External Customers and Long-Lived Assets [Line Items]
Distance from city	15