Revenue (Details 3) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of revenue by performance obligation
Operating revenue	$ 621,458	$ 448,564	$ 1,193,618	$ 847,880
Management fee revenue, policy issuance and renewal services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	454,572	441,319	860,550	833,377
Management fee revenue, policy issuance and renewal services [Member] | Transferred at point in time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	454,572	$ 441,319	860,550	$ 833,377
Management fee revenue, administrative services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	13,299		26,373
Management fee revenue, administrative services [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	13,299		26,373
Administrative services reimbursements [Member]
Disaggregation of revenue by performance obligation
Operating revenue	146,507		292,470
Administrative services reimbursements [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	146,507		292,470
Administrative services [Member]
Disaggregation of revenue by performance obligation
Operating revenue	159,806		318,843
Administrative services [Member] | Transferred over time [Member]
Disaggregation of revenue by performance obligation
Operating revenue	$ 159,806		$ 318,843