Senior Unsecured Notes and Secured Debt (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Secured debt principal activity
Secured debt issued	$ 10,690,000	$ 0
Secured debt extinguished	129,539,000	18,931,000
Excluding Fair Value Adjustments [Member]
Secured debt principal activity
Secured debt principal balance	2,875,957,000	2,425,033,000	3,010,711,000	2,311,586,000
Secured debt issued	10,690,000	0
Secured debt assumed	0	132,680,000
Secured debt extinguished	(114,084,000)	(7,807,000)
Secured debt principal payments	(15,455,000)	(11,432,000)
Secured debt foreign currency	$ (15,905,000)	$ 6,000
Secured debt principal balance average rate	0.0508	0.0517	0.051	0.0514
Secured debt principal issued average rate	0.0354	0
Secured debt principal assumed average rate	0	0.0549
Secured debt principal extinguished average rate	0.0573	0.0743
Secured debt principal payment average rate	0.0512	0.0544
Secured debt principal foreign currency average rate	0.0386	0.0562