Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 81,946	$ 63,060
Initial deferred tax liability related to 2018 convertible debt	9,793	12,032
Unrecognized tax benefits	3,712	2,983	$ 2,141	$ 1,101
Uncertain tax positions that would impact the effective tax rate	100
Domestic Tax Authority | Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	273,900
Operating loss carryforwards, Sec. 382 limitation	4,200
Net operating loss carryforwards	269,800
Operating loss carryforwards, subject to expiration	170,600
Operating loss carryforwards, not subject to expiration	103,300
State and Local Jurisdiction | Arizona Department of Revenue
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 253,900
Convertible Debt
Operating Loss Carryforwards [Line Items]
Initial deferred tax liability related to 2018 convertible debt		$ 14,000