Share-Based Compensation (Narrative) (Details) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Incentive Stock Options [Member]	Dec. 31, 2011 Non-Qualified Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2011 1997 Plan [Member]	Dec. 31, 2011 2005 Plan [Member]	May 31, 2005 2005 Plan [Member]	Dec. 31, 2011 Expected to be recognized during 2012 [Member] Stock Options [Member]	Dec. 31, 2011 Expected to be recognized during 2012 [Member] Restricted Stock [Member]	Dec. 31, 2011 Expected to be recognized during 2013 [Member] Stock Options [Member]
Exercise price, minimum percentage				100.00%	100.00%
Common stock on date granted term period, years								10
Shares available for grants								360,635	1,500,000
Combined share-based compensation expense for 2005 Plan and 1997 Plan	$ 3,087,000	$ 2,368,000	$ 853,000
Term of options outstanding, years							5
Expenses, stock options	3,077,000	2,343,000	801,000
Expenses, restricted stock	10,000	25,000	52,000
Unrecognized compensation cost						453,000				406,000	1,000	47,000
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Date				ten
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.91	$ 6.26	$ 3.20
Contractual Life, Weighted Average, Outstanding	4.69
Number of shares authorized	870,057
Intrinsic Value, Outstanding	993,000
Intrinsic Value per Share, Outstanding	$ 1.95
Intrinsic Value, Exercisable	692,000
Intrinsic Value per Share, Exercisable	$ 2.06
Intrinsic Value, Exercises in Period	$ 2,567,000	$ 3,510,000	$ 2,136,000
Intrinsic Value per Share, Exercises in Period	$ 12.94	$ 13.28	$ 11.81
Closing Market Price of NHI Common Stock	$ 43.98