Revenue (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of revenue by performance obligation
Operating revenue	$ 612,126	$ 442,492	$ 1,805,744	$ 1,290,372
Management fee revenue, policy issuance and renewal services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	451,361	435,214	1,311,911	1,268,591
Management fee revenue, policy issuance and renewal services [Member] | Transferred at point in time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	451,361	$ 435,214	1,311,911	$ 1,268,591
Management fee revenue, administrative services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	13,521		39,894
Management fee revenue, administrative services [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	13,521		39,894
Administrative services reimbursements [Member]
Disaggregation of revenue by performance obligation
Operating revenue	140,172		432,642
Administrative services reimbursements [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	140,172		432,642
Administrative services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	153,693		472,536
Administrative services [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	$ 153,693		$ 472,536