Mergers and Acquisitions - Medistem - Fair Value of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 157,175	$ 165,169	$ 101,059
Medistem, Inc.
Business Acquisition [Line Items]
Cash				$ 8
Intangible assets				4,824
Total assets acquired				4,832
Accounts payable				644
Accrued compensation and benefits				67
Other accrued liabilities				50
Total liabilities assumed				761
Net assets acquired				4,071
Goodwill				20,924
Total consideration and fair value of noncontrolling interest				$ 24,995