2. Significant Accounting Policies Schedule of Redeemable Noncontrolling Interests - Operating Partnership (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accounting Policies [Abstract]
Balance at December 31, 2012, units			18,786,806
Balance at December 31, 2012			$ 453,889
Net income attributable to redeemable noncontrolling interests – operating partnership	(2,541)	2,181	2,397	5,757
Distributions declared			(11,132)
Redemption of operating partnership units, shares			(2,904,769)
Redemption of operating partnership units			(70,200)	(5,700)
Adjustments to redeemable noncontrolling interests – operating partnership			34,326	21,643
Balance at March 31, 2013, units	15,882,037		15,882,037
Balance at March 31, 2013	$ 409,280		$ 409,280