Equity and Stock Based-Compensation (Details Textual 1) (USD $)	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2006 Employee
Equity (Textual) [Abstract]
Stock options outstanding	5,960,000	6,460,000
Compensation expense, options	$ 2,359,000	$ 4,395,000	$ 5,705,000
Share-based Compensation Arrangement by Share-based Payment Award additional (Textual) [Abstract]
Shares authorized under stock option plan	1,017,005
Stock option exercised	4,000
Weighted average contractual life of outstanding options	3.9
Weighted average contractual life of exercisable options	3.4
Percentage of average market price used to determine number of shares directors receive in lieu of cash fees	95.00%
Shares of stock in lieu of cash for director fees	30,005	35,040	29,007
Percentage of restrictions on the ownership of the Company's total common and preferred stock	3.90%
Number of share under the RSU Plan that gives the right to receive payment in cash equal to the fair market value	1
Number of trailing months used as basis of second RSU	12 years
Other Stock Option [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted	214,206
Three years from grant date [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted	29,411
Immediately on the grant date [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted	52,416
Stock Options [Member]
Equity (Textual) [Abstract]
Stock options outstanding	5,959,662
Term life of stock options	10 years
Vesting period of restricted stock units	4 years
Compensation expense, options	941,000	1,600,000	2,000,000
Additional compensation expense in connection with retirement of executives		110,000	872,000
Unrecognized compensation cost	961,000
Recognition period of future compensation expense over weighted average	2.5
Exercise period of option after employee termination	1 year
Employee Service Share-based Compensation, Cash Received from Exercise of Stock Options	34,000
Share-based compensation arrangement outstanding	0
Share-based compensation arrangement exercisable	0
Restricted Stock [Member]
Equity (Textual) [Abstract]
Vesting period of restricted stock units	3 years
Compensation expense, restricted stock	1,200,000	747,000	433,000
Additional compensation expense in connection with retirement of executives		129,000	298,000
Unrecognized compensation cost	1,900,000
Unrecognized compensation cost, period for recognition	1.8
Total fair value of the restricted stock which vested	43,000
Number of restricted stock units granted	244,000
Restricted Stock [Member] | Other Stock Option [Member]
Equity (Textual) [Abstract]
Vesting period of restricted stock units	4 years
Restricted Stock Units (RSUs) [Member]
Equity (Textual) [Abstract]
Vesting period of restricted stock units	4 years
Vesting period of restricted stock units	3 years
Number of restricted stock units granted	57,000
Restricted Stock Units (RSUs) [Member] | Three years from grant date [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted		20,368
Restricted Stock Units (RSUs) [Member] | Four years from grant date [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted	401	21,442
Non-performance-based Restricted Stock Units (RSUs) [Member] | Three years from grant date [Member]
Equity (Textual) [Abstract]
Number of restricted stock units granted	56,845
Performance-based RSU [Member]
Equity (Textual) [Abstract]
Performance based RSUs outstanding		172,489
Vesting period of restricted stock units	February 15, 2013			5 years
Recognized compensation expense related to RSUs for employees and directors, before capitalization or income tax benefit, if any	1,000,000	1,200,000	1,100,000
Additional compensation expense in connection with retirement of executives		153,000	413,000
Unrecognized compensation cost, period for recognition	1.9
Number of restricted stock units granted	164,000
Total cash paid for regular RSU vesting and dividend payments	445,000
Number of company type awards to key employees				2
Performance period	January 1, 2011 to December 31, 2013
Payout range minimum	0.00%
Payout range maximum	200.00%
Payout per unit average 30 days closing price	30 days
Estimate of future expense for all types of RSUs outstanding	1,400,000
MSCI RSUs [Member]
Equity (Textual) [Abstract]
Performance based RSUs outstanding		76,324
EBITDA RSUs [Member]
Equity (Textual) [Abstract]
Performance based RSUs outstanding		109,898
SNL RSUs [Member]
Equity (Textual) [Abstract]
Performance based RSUs outstanding	96,149
FFO RSUs [Member]
Equity (Textual) [Abstract]
Performance based RSUs outstanding	61,810
Long-term incentive compensation [Member]
Equity (Textual) [Abstract]
Compensation expense, options	$ (767,000)	$ 805,000	$ 500,000
7.75% Series A Cumulative Redeemable Preferred Stock [Member]
Equity (Textual) [Abstract]
Preferred stock, shares outstanding	2,993,090
Liquidation preference per share	$ 25
Preferred stock, dividend rate	7.75%
7.50% Series B Cumulative Redeemable Preferred Stock [Member]
Equity (Textual) [Abstract]
Preferred stock, shares outstanding	3,791,000
Liquidation preference per share	$ 25
Preferred stock, dividend rate	7.50%