Commitments and Contingencies (Narrative) (Details) ft² in Thousands, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jun. 30, 2017 USD ($) ft²	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) ft²	Jun. 30, 2016 USD ($)
Operating Leased Assets [Line Items]
Rent expense		$ 1,000	$ 900	$ 1,900	$ 1,600
Settlement costs from litigation		0	0	0	4,650
Termination costs		$ 7,906	23,228	$ 23,568	61,631
Contract Termination
Operating Leased Assets [Line Items]
Termination costs			$ 1,100		$ 2,700
Minimum
Operating Leased Assets [Line Items]
Severance payment, prior to change in control				6 months
Severance payment, period following change in control				18 months
Maximum
Operating Leased Assets [Line Items]
Severance payment, prior to change in control				18 months
Severance payment, period following change in control				24 months
TriVascular Technologies, Inc. | Manufacturing Facility
Operating Leased Assets [Line Items]
Aggregate square feet | ft²		110		110
Subsequent Event | TriVascular Technologies, Inc.
Operating Leased Assets [Line Items]
Renewal term	5 years