Notes Receivable and Other Long-term Receivables (Narrative) (Detail) $ / shares in Units, $ in Thousands, shares in Millions														1 Months Ended	3 Months Ended			12 Months Ended	58 Months Ended
		Sep. 21, 2017 USD ($)	Feb. 14, 2017 USD ($)	Feb. 09, 2017 USD ($)	Feb. 06, 2017 USD ($)	Dec. 30, 2016 USD ($)	Jul. 16, 2016 $ / shares	Sep. 22, 2015 USD ($)	Jun. 26, 2015 USD ($) $ / shares shares	Nov. 10, 2014 USD ($)	Nov. 05, 2013 USD ($)	Oct. 03, 2013 USD ($)	Aug. 15, 2013 USD ($)	Jan. 31, 2013 USD ($)	Mar. 31, 2018 USD ($)		Mar. 31, 2017 USD ($)	Dec. 31, 2013 USD ($)	Apr. 30, 2018	Feb. 02, 2018 $ / shares shares	Dec. 31, 2017 USD ($)		Nov. 14, 2016 USD ($)	Sep. 29, 2016 $ / shares	Sep. 12, 2016 USD ($) $ / shares	Jul. 15, 2016 USD ($)	Dec. 31, 2015 USD ($) $ / shares	Dec. 15, 2015 USD ($) shares	Oct. 07, 2015 $ / shares	Sep. 29, 2015 USD ($)	May 12, 2015 USD ($)	Nov. 09, 2014	Sep. 30, 2014 USD ($)	Apr. 01, 2014 USD ($)	Nov. 06, 2013 USD ($)	Jun. 28, 2013 USD ($)	Mar. 05, 2013 USD ($)	Nov. 02, 2012 USD ($)	Jan. 27, 2012 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Premiums, Percentage Assumed to Net		1.00%
Investment Warrants, Exercise Price | $ / shares							$ 0.01
Repayment of notes receivable															$ 0		$ 7,890
Accounts Receivable, Net, Noncurrent	[1]														1,400
Investment Owned, Balance, Shares | shares																												1.7
Investment Owned, at Cost															6,600
Commitments and Contingencies																[1]						[2]					$ 500				$ 8,500
Equity investment, shares held (shares) | shares																				4.4
Warrants and Rights Outstanding															100						$ 29
Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																																	$ 53,900
Gain Contingency, Unrecorded Amount															55,800
Financing Receivable, Net															50,200
Interest rate of note receivable (in Percent)													5.00%
Avinger [Member]
Accounts Notes And Loans Receivable [Line Items]
Repayment of notes receivable								$ 21,400
LENSAR [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross												$ 40,000																$ 42,000
Interest rate of note receivable (in Percent)												15.50%																			18.50%
Amount company has agreed to advance under agreement												$ 60,000
Alphaeon [Member]
Accounts Notes And Loans Receivable [Line Items]
Investment estimated fair value, per share | $ / shares																											$ 3.84
DirectFlow [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																							$ 1,000		$ 1,500	$ 1,500									$ 35,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down						$ 51,100
Proceeds from Sale of Other Assets			$ 700	$ 500	$ 7,000
Interest rate of note receivable (in Percent)																																13.50%			15.50%
Amount company has agreed to advance under agreement										$ 15,000	$ 50,000
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares																								$ 0.01	$ 0.01
Hyperion [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																																							$ 2,300
Number of payments to be received																																							2
Periodic contractual payments																																					$ 1,200
kaleo Note Receivable [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																																		$ 150,000
Repayment of notes receivable		$ 141,700
CareView [Member]
Accounts Notes And Loans Receivable [Line Items]
Interest rate of note receivable (in Percent)									13.50%
Amount company has agreed to advance under agreement									$ 40,000
Tranche 1 of note receivable									20,000
Tranche 2 of note receivable									$ 20,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights | shares									4.4
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares									$ 0.45											$ 0.03									$ 0.40
Warrants and Rights Outstanding															$ 100
Credit Agreement [Member] | Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																																						$ 40,000
Credit agreement, stated interest rate (in Percent)																																						5.00%
Proceeds received under remedies available for borrower's breach of terms credit agreement														$ 8,100
Amount company has agreed to advance under agreement																		$ 8,700
Financing Receivable, Modifications, Post-Modification Recorded Investment													$ 44,100
Credit Agreement [Member] | LENSAR [Member]
Accounts Notes And Loans Receivable [Line Items]
Amount company has agreed to advance under agreement					$ 2,800
Initial Loan [Member] | Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing Receivable, Modifications, Pre-Modification Recorded Investment													33,700
Additional Loan [Member]
Accounts Notes And Loans Receivable [Line Items]
Commitments and Contingencies																														$ 800
Additional Loan [Member] | Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																																				$ 1,300
Additional Loan [Member] | LENSAR [Member]
Accounts Notes And Loans Receivable [Line Items]
Amount company has agreed to advance under agreement												$ 20,000
Royalty Agreement [Member] | Avinger [Member]
Accounts Notes And Loans Receivable [Line Items]
Reduction in royalty rate (in percent)																			50.00%
Term loan and interest [Member] | Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing Receivable, Modifications, Pre-Modification Recorded Investment													1,300
Forbearance principal and interest [Member] | Wellstat Diagnostics [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing Receivable, Modifications, Pre-Modification Recorded Investment													$ 9,100
Tranche three [Member] | DirectFlow [Member]
Accounts Notes And Loans Receivable [Line Items]
Financing receivable, gross																												$ 5,000

[1] unaudited

[2] Note 1