Discontinued Operations - Income from Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefits and expenses:
Gain from sale of discontinued operations										$ 1,800
Income from discontinued operations	$ (30)	$ (12)	$ (90)	$ (3,637)	$ 10,636	$ 9,959	$ (865)	$ (9,541)	$ (3,769)	10,189	$ 10,807
Income taxes paid									74,379	79,790	110,650
Medicare Part D
Revenue:
Health premium									0	222,840	260,657
Benefits and expenses:
Health policyholder benefits									3,827	183,423	213,114
Amortization of deferred acquisition costs									0	3,747	3,506
Commissions, premium taxes, and non-deferred acquisition expenses									763	16,396	20,909
Other operating expense									1,209	5,377	6,502
Total benefits and expenses									5,799	208,943	244,031
Income before income taxes for discontinued operations									(5,799)	13,897	16,626
Gain from sale of discontinued operations									0	1,779	0
Income taxes									2,030	(5,487)	(5,819)
Income from discontinued operations									(3,769)	10,189	10,807
Discontinued Operations | Medicare Part D
Benefits and expenses:
Income taxes paid									$ 714	$ 15,271	$ 3,409