Fair Value Measurements (Schedule of Fair Value of Assets and Liabilities not Subject to Fair Value Recognition) (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Assets
Notes receivable, Carrying Value	$ 418,578,000	$ 195,048,000
Liabilities:
Convertible Notes Payable, Carrying Value	492,901,000	395,280,000
Series 2012 Notes [Member]
Liabilities:
Convertible Notes Payable, Carrying Value	47,564,000	172,630,000
May 2015 Notes [Member]
Liabilities:
Convertible Notes Payable, Carrying Value	152,105,000	148,253,000
February 2018 Notes [Member]
Liabilities:
Convertible Notes Payable, Carrying Value	274,512,000	0
Term Loan. [Member]
Liabilities:
Convertible Notes Payable, Carrying Value	18,720,000	74,397,000
Wellstat Note Receivable [Member]
Assets
Notes receivable, Carrying Value	50,191,000	47,694,000
Hyperion [Member]
Assets
Notes receivable, Carrying Value	1,200,000	1,194,000
AxoGen Note Receivable [Member]
Fair Value by Balance Sheet Grouping [Line Items]
Embedded Derivative, Fair Value of Embedded Derivative Asset	1,200,000	1,100,000
Assets
Notes receivable, Carrying Value	30,192,000	26,544,000
Avinger Note Receivable [Member]
Assets
Notes receivable, Carrying Value	20,516,000	20,250,000
LENSAR Note Receivable [Member]
Assets
Notes receivable, Carrying Value	39,645,000	39,572,000
Durata Note Receivable [Member]
Assets
Notes receivable, Carrying Value	40,000,000	24,995,000
Direct Flow Medical Note Receivable [Member]
Assets
Notes receivable, Carrying Value	35,212,000	34,799,000
Paradigm Spine [Member]
Assets
Notes receivable, Carrying Value	49,544,000	0
kaleo Note Receivable [Member]
Assets
Notes receivable, Carrying Value	152,078,000	0
Notes receivable, Fair Value		0
Fair Value Level 2 [Member]
Liabilities:
Notes payable, Fair Value	577,836,000	564,954,000
Fair Value Level 2 [Member] | Series 2012 Notes [Member]
Liabilities:
Notes payable, Fair Value	69,172,000	277,650,000
Fair Value Level 2 [Member] | May 2015 Notes [Member]
Liabilities:
Notes payable, Fair Value	197,354,000	212,304,000
Fair Value Level 2 [Member] | February 2018 Notes [Member]
Liabilities:
Notes payable, Fair Value	292,560,000
Fair Value Level 2 [Member] | Term Loan. [Member]
Liabilities:
Notes payable, Fair Value	18,750,000	75,000,000
Fair Value Level 2 [Member] | Hyperion [Member]
Assets
Notes receivable, Fair Value	0	0
Fair Value Level 2 [Member] | LENSAR Note Receivable [Member]
Assets
Notes receivable, Fair Value	0	0
Fair Value Level 2 [Member] | Durata Note Receivable [Member]
Assets
Notes receivable, Fair Value	0	0
Fair Value Level 2 [Member] | Direct Flow Medical Note Receivable [Member]
Assets
Notes receivable, Fair Value	0	0
Fair Value Level 2 [Member] | Paradigm Spine [Member]
Assets
Notes receivable, Fair Value	0	0
Fair Value Level 2 [Member] | kaleo Note Receivable [Member]
Assets
Notes receivable, Fair Value	0
Fair Value Level 3 [Member]
Assets
Notes receivable, Fair Value	420,123,000	191,449,000
Fair Value Level 3 [Member] | Wellstat Note Receivable [Member]
Assets
Notes receivable, Fair Value	50,191,000	46,042,000
Fair Value Level 3 [Member] | Hyperion [Member]
Assets
Notes receivable, Fair Value	1,200,000	1,195,000
Fair Value Level 3 [Member] | AxoGen Note Receivable [Member]
Assets
Notes receivable, Fair Value	29,303,000	25,785,000
Fair Value Level 3 [Member] | Avinger Note Receivable [Member]
Assets
Notes receivable, Fair Value	19,746,000	19,061,000
Fair Value Level 3 [Member] | LENSAR Note Receivable [Member]
Assets
Notes receivable, Fair Value	40,000,000	39,572,000
Fair Value Level 3 [Member] | Durata Note Receivable [Member]
Assets
Notes receivable, Fair Value	40,000,000	24,995,000
Fair Value Level 3 [Member] | Direct Flow Medical Note Receivable [Member]
Assets
Notes receivable, Fair Value	36,752,000	34,799,000
Fair Value Level 3 [Member] | Paradigm Spine [Member]
Assets
Notes receivable, Fair Value	50,791,000	0
Fair Value Level 3 [Member] | kaleo Note Receivable [Member]
Assets
Notes receivable, Fair Value	$ 152,140,000