Income per Common Share of the Trust (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Dilutive Shares, Shares Issued, Shares Acquired on Exchange [Abstract]
Common Units Exchanged																	157,285	94,895	119,987
Stock Options Exercised																	504,000	841,000	256,000
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	959,000	905,000	1,685,000
Common Stock, Dividends, Per Share, Declared																	$ 1.90	$ 1.90	$ 1.90
Income per Common Share of the Trust [Abstract]
Income from continuing operations net of noncontrolling interest																	$ 91,274	$ 88,008	$ 81,392
Weighted Average Shares, Diluted																	130,909,000	117,694,000	115,503,000
Income from Continuing Operations, Per Diluted Share																	$ 0.70	$ 0.75	$ 0.70
Dilutive shares for long-term compensation plans																	729,000	831,000	748,000
Discontinued operations net of noncontrolling interest, per share, diluted																	$ 0.90	$ 0.42	$ 0.89
Net Income Available to Common Shareholders, Basic																	209,738	137,436	183,999
Weighted Average Number of Shares Outstanding, Basic																	130,180,000	116,863,000	114,755,000
Earnings Per Share, Basic	$ 0.48	[1]	$ 0.21	[1]	$ 0.33	[1]	$ 0.60	[1]	$ 0.33	[1]	$ 0.24	[1]	$ 0.29	[1]	$ 0.32	[1]	$ 1.61	$ 1.18	$ 1.60
Discontinued operations net of noncontrolling interest, per share, basic																	$ 0.91	$ 0.43	$ 0.89
Earnings Per Share, Diluted	$ 0.48	[1]	$ 0.21	[1]	$ 0.33	[1]	$ 0.60	[1]	$ 0.32	[1]	$ 0.24	[1]	$ 0.29	[1]	$ 0.32	[1]	$ 1.60	$ 1.17	$ 1.59
Income from continuing operations net of noncontrolling interest, per share, basic																	$ 0.70	$ 0.75	$ 0.71
Discontinued operations net of noncontrolling interest																	$ 118,464	$ 49,428	$ 102,607

[1] The sum of quarterly financial data may vary from the annual data due to rounding.