CONSOLIDATED STATEMENT OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total
Balance at Dec. 31, 2014	$ 0	$ 35	$ 292,346	$ 42,439	$ (28,182)	$ (2,048)	$ 304,590
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	0	0	0	(31,318)	0	(2,191)	(33,509)
Exercise of stock options	0	1	2,466	0	0	0	2,467
Repurchase of common stock	0	0	0	(1,833)	0	0	(1,833)
Tax effect of stock options and restricted stock units	0	0	(5,617)	0	0	0	(5,617)
Share-based employee compensation expense	0	0	10,469	0	0	0	10,469
Issuance of CareFirst Warrants	0	0	2,408	0	0	0	2,408
Proceeds from non-controlling interest	0	0	1,615	0	0	0	1,615
Balance at Dec. 31, 2015	0	36	303,687	9,288	(28,182)	(4,239)	280,590
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	0	0	0	(128,615)	0	(263)	(128,878)
Exercise of stock options	0	2	10,000	0	0	0	10,002
Tax effect of stock options and restricted stock units	0	0	(8,947)	0	0	0	(8,947)
Share-based employee compensation expense	0	0	17,538	0	0	0	17,538
Issuance of CareFirst Warrants	0	0	192	0	0	0	192
Conversion of CareFirst Convertible Note	0	1	19,999	0	0	0	20,000
Settlement of non-controlling interest	0	0	(1,199)	0	0	0	(1,199)
Balance at Dec. 31, 2016	0	39	341,270	(119,327)	(28,182)	(4,502)	189,298
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of a change in accounting principle - adoption of ASU 2016-09 | Accounting Standards Update 2016-09 [Member]	0	0	74	6,464	0	0	6,538
Comprehensive income (loss)	0	0	0	63,715	0	4,502	68,217
Exercise of stock options	0	1	5,722	0	0	0	5,723
Tax withholding for share-based compensation	0	0	(4,481)	0	0	0	(4,481)
Share-based employee compensation expense	0	0	6,658	0	0	0	6,658
Balance at Dec. 31, 2017	$ 0	$ 40	$ 349,243	$ (49,148)	$ (28,182)	$ 0	$ 271,953