Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	COMMON STOCK, AMOUNT	PAID-IN CAPITAL	ACCUMULATED OTHER COMPREHENSIVE INCOME(LOSS)	TREASURY STOCK, AT COST	RETAINED EARNINGS	TOTAL IHC STOCKHOLDERS' EQUITY	NON-CONTROLLING INTERESTS
Treasury Stock, Shares					(1,517,983)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2016	$ 439,256	$ 18,620	$ 126,468	$ (6,964)	$ (17,483)	$ 315,918	$ 436,559	$ 2,697
Common Stock, Shares, Outstanding, Beginning Balance at Dec. 31, 2016		18,620,508
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	42,069					42,042	42,042	27
Other Comprehensive Income (Loss), Net of Tax	3,181			3,181			3,181	0
Treasury Stock, Value, Acquired, Cost Method	$ (46,527)				$ (46,527)		(46,527)	0
Treasury Stock, Shares, Acquired	(2,289,502)				(2,289,502)
Dividends, Common Stock, Cash	$ (2,392)					(2,392)	(2,392)	0
Sharebased Compensation Effect On Stockholders Equity	(1,319)	$ 5	(1,930)		$ 606		(1,319)	0
Sharebased Compensation Effect On Stockholders Equity, Shares Issued		4,950			72,312
Distributions to noncontrolling interests	(25)						0	(25)
Stockholders Equity, Reclassification Of Stranded Tax Effects In Accumulated Other Comprehensive Income	0			(815)		815	0	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Dec. 31, 2017	$ 434,243	$ 18,625	124,538	(4,598)	$ (63,404)	356,383	431,544	2,699
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2017	14,890,285	18,625,458
Treasury Stock, Shares	(3,735,173)				(3,735,173)
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	$ 28,834					28,482	28,482	352
Other Comprehensive Income (Loss), Net of Tax	(3,362)			(3,362)			(3,362)	0
Treasury Stock, Value, Acquired, Cost Method	$ (4,019)				$ (4,019)		(4,019)	0
Treasury Stock, Shares, Acquired	(135,311)				(135,311)
Dividends, Common Stock, Cash	$ (4,468)					(4,468)	(4,468)	0
Sharebased Compensation Effect On Stockholders Equity	888		(143)		$ 1,031		888	0
Sharebased Compensation Effect On Stockholders Equity, Shares Issued					123,274
Distributions to noncontrolling interests	(272)						0	(272)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Dec. 31, 2018	$ 451,431	$ 18,625	$ 124,395	(8,310)	$ (66,392)	380,431	448,749	2,682
Common Stock, Shares, Outstanding, Ending Balance at Dec. 31, 2018	14,878,248	18,625,458
Treasury Stock, Shares	(3,747,210)				(3,747,210)
Cumulative Effect of New Accounting Principle in Period of Adoption	$ (413)			$ (350)		$ 34	$ (316)	$ (97)