Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Goodwill	$ 152,459,000		$ 152,459,000		$ 152,459,000
Intangibles, net	88,371,000		88,371,000		$ 101,626,000
Indefinite lived intangible, insurance licenses	1,300,000		1,300,000
Amortization of intangible assets	$ 6,600,000	$ 558,000	13,300,000	$ 3,000,000
Impairment of amortizing intangible assets			0	0
Impairment of non-amortizing intangible assets			$ 0	$ 0
NBIC [Member]
Finite Lived Intangible Assets [Line Items]
Estimated value of business acquired			1 year
Minimum [Member]
Finite Lived Intangible Assets [Line Items]
Useful life of intangible asset			2 years 6 months
Maximum [Member]
Finite Lived Intangible Assets [Line Items]
Useful life of intangible asset			15 years