Marketable Securities and Derivative Instruments: Derivative Instruments (Narratives) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended			0 Months Ended		3 Months Ended							0 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 19, 2013 JC Penney [Member]	Mar. 04, 2013 JC Penney [Member]	Mar. 31, 2013 JC Penney [Member]	Dec. 31, 2013 JC Penney [Member]	Dec. 31, 2012 JC Penney [Member]	Mar. 31, 2013 Lexington Realty Trust [Member] Maximum [Member]	Mar. 31, 2013 Lexington Realty Trust [Member] Minimum [Member]	Mar. 31, 2013 Shares Owned [Member] JC Penney [Member]	Dec. 31, 2012 Forward Contracts [Member] JC Penney [Member]	Sep. 19, 2013 Common Shares [Member] JC Penney [Member]	Dec. 31, 2012 Common Shares [Member] JC Penney [Member]	Dec. 31, 2013 Other Investments [Member]	Dec. 31, 2012 Other Investments [Member]	Dec. 31, 2011 Other Investments [Member]
Derivative [Line Items]
Ownership Percentage									17.20%	8.80%
Ownership common shares, investee								23,400,000			8,584,010	4,815,990		18,584,010
Closing share price (in dollars per share)						$ 15.11								$ 19.71
Investment Owned, at Cost												$ 141,309		$ 366,291
Strike price of common shares held under forward contract (in dollars per share)												$ 29.34
Sale of Stock, Number of Shares				13,400,000	10,000,000
Sale price, per share (in dollars per share)				$ 13.00	$ 16.03
Net loss on sale of common shares in J.C Penney				(18,114)	(36,800)										31,741	3,582	5,020
Non-cash impairment loss on J.C. Penney common shares	39,487	224,937	0			39,487
Receipt of common shares by settling forward contract													4,815,990
Unrealized Gain Loss On Derivatives	(33,487)	(75,815)	12,984										(33,487)
Marketable Securities Net Economic Gain Loss							(256,156)
Proceeds from sales of, and return of investment in, marketable securities	$ 378,709	$ 60,258	$ 70,418	$ 174,200	$ 160,300										$ 44,209	$ 58,718	$ 69,559