Income Tax Expense (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 03, 2016
Operating Loss Carryforwards [Line Items]
U.S. Federal statutory rate to net income (loss) before taxes	34.00%
Deferred tax assets, valuation allowance	$ 133,784	$ 67,172
Change in valuation allowance	66,600
Net change in valuation allowance, recorded as tax expense	35,678	10,052	$ 8,930
Deferred tax asset related to compensation benefits as well as Federal and State net operating loss carryforwards	10,300
Decrease in net operating loss carryforwards	(124,881)	(66,280)
Decrease in research and development credits	(21,374)	(8,948)
Undistributed earnings of foreign subsidiaries	119
Provision for income taxes	$ 498	$ (9,337)	$ (62)
Effective tax rate	0.32%
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, domestic	$ 300,400
Internal Revenue Service (IRS) | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward amount	9,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, state and local	185,200
State and Local Jurisdiction | Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Tax credit carryforward amount	13,400
Income Tax Expense (Benefit)
Operating Loss Carryforwards [Line Items]
Net change in valuation allowance, recorded as tax expense	35,700
TriVascular Technologies, Inc. | Income Tax Expense (Benefit)
Operating Loss Carryforwards [Line Items]
Net change in valuation allowance, recorded as tax expense	$ 30,900
Scenario, Adjustment | TriVascular Technologies, Inc.
Operating Loss Carryforwards [Line Items]
Decrease in research and development credits				$ 3,100
Scenario, Adjustment | TriVascular Technologies, Inc. | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Decrease in net operating loss carryforwards				210,600
Scenario, Adjustment | TriVascular Technologies, Inc. | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Decrease in net operating loss carryforwards				$ 230,300