Immaterial Corrections to Prior Period Financial Statements (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Increase in selling, operating and administrative expenses									$ 107,268,000	$ 88,213,000	$ 91,561,000
Decrease in net income	$ (1,934,000)	$ (7,537,000)	$ (15,637,000)	$ (10,071,000)	$ (8,397,000)	$ (14,306,000)	$ (14,128,000)	$ (10,395,000)	(35,179,000)	(47,226,000)	(50,775,000)
Increase in additional paid-in capital	451,199,000				448,713,000				451,199,000	448,713,000
Decrease in retained earnings	(16,027,000)				(16,005,000)				(16,027,000)	(16,005,000)
Decrease in non controlling interest	$ 398,348,000				403,983,000				$ 398,348,000	403,983,000
Revision Of Selling Operating And Administrative Expense [Member] | Restatement Adjustment [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Increase in selling, operating and administrative expenses										584,000	575,000
Decrease in net income										584,000	$ 575,000
Increase in additional paid-in capital					1,712,000					1,712,000
Decrease in retained earnings					803,000					803,000
Decrease in non controlling interest					$ 909,000					$ 909,000
Adjustment to consolidated balance sheet												$ 553,000