Income Taxes - Reconciliation of The Statutory Federal Rate and The Company's Effective Tax Rate (Details)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax provision (benefit) at federal statutory rate	(21.00%)	(34.00%)	(34.00%)
State income taxes, net of federal benefit	0.32%	1.94%	2.99%
Effect of noncontrolling and redeemable noncontrolling interests	24.01%	51.03%	50.88%
Stock-based compensation	(1.77%)	0.70%	0.69%
Effect of prepaid tax asset	(0.00%)	(0.00%)	0.50%
Tax credits	(1.35%)	(1.25%)	(1.63%)
Effect of federal rate change	(0.00%)	(15.93%)	(0.00%)
Effect of valuation allowance	3.04%	0.81%	0.25%
Other	0.47%	1.20%	1.58%
Total	3.72%	4.50%	21.26%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

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-Name Accounting Standards Codification
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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to noncontrolling interest income (loss) exempt from income taxes.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to revisions of previously reported income tax expense.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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