Derivative and Other Fair Value Instruments (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	$ 11,428	$ 18,710
Fair Value Of Serp Investments	88,010	83,845
Assets, Fair Value Disclosure	99,438	102,555
Derivative liability, fair value	4,670
Other Liabilities, Fair Value Disclosure	88,010	83,845
Liabilities, Fair Value Disclosure	92,680	83,845
Redeemable Noncontrolling Interest Operating Partnership Liability Fair Value Disclosure	405,276	363,144
Fair Value, Inputs, Level 1 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	0	0
Fair Value Of Serp Investments	88,010	83,845
Assets, Fair Value Disclosure	88,010	83,845
Derivative liability, fair value	0
Other Liabilities, Fair Value Disclosure	88,010	83,845
Liabilities, Fair Value Disclosure	88,010	83,845
Redeemable Noncontrolling Interest Operating Partnership Liability Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	11,428	18,710
Fair Value Of Serp Investments	0	0
Assets, Fair Value Disclosure	11,428	18,710
Derivative liability, fair value	4,670
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	4,670	0
Redeemable Noncontrolling Interest Operating Partnership Liability Fair Value Disclosure	405,276	363,144
Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative asset, fair value	0	0
Fair Value Of Serp Investments	0	0
Assets, Fair Value Disclosure	0	0
Derivative liability, fair value	0
Other Liabilities, Fair Value Disclosure	0	0
Liabilities, Fair Value Disclosure	0	0
Redeemable Noncontrolling Interest Operating Partnership Liability Fair Value Disclosure	$ 0	$ 0