Acquisitions - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 01, 2017	Dec. 31, 2016	Oct. 30, 2015
Business Acquisition [Line Items]
Goodwill	$ 117,589		$ 79,648
Advantage RN, LLC
Business Acquisition [Line Items]
Cash and cash equivalents		$ 2,833
Accounts receivable		14,396
Other current assets		392
Property and equipment		333
Goodwill		43,596
Other intangible assets		29,900
Total assets acquired		91,450
Accounts payable and accrued expenses		368
Accrued employee compensation and benefits		1,685
Other current liabilities		2
Total liabilities assumed		2,055
Net assets acquired		$ 89,395
Mediscan
Business Acquisition [Line Items]
Cash and cash equivalents				$ 79
Accounts receivable				6,851
Other current assets				140
Property and equipment				20
Goodwill				14,338
Other intangible assets				17,200
Total assets acquired				38,628
Accounts payable and accrued expenses				306
Accrued employee compensation and benefits				1,410
Total liabilities assumed				1,716
Net assets acquired				$ 36,912