Acquisitions and Disposals - Brooklyn Acquisition narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired		$ 28,948	$ 315,000	$ 18,500
Brooklyn Underwriting Pty Limited and Brooklyn IT Pty Limited [Member]
Business Acquisition [Line Items]
Finite-lived Intangible Assets Acquired	$ 22,900