Business Combinations Purchase Price Allocation (Details) (Parent Company [Member], Colonial [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	$ 4,062,421
Business Acquisition, PPA, Liabilities Assumed	1,899,545
Business Acquisition, Cost of Acquired Entity, Purchase Price	2,162,876
Land [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	469,396
Building and Building Improvements [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	3,075,642
Furniture Fixtures And Equipment [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	96,377
Construction in Progress [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	113,368
Unimproved Land [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	58,400
Assets Held-for-sale [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	33,300
Finite-Lived Intangible Assets, Major Class Name [Domain]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	57,946
Cash and Cash Equivalents [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	63,454
Restricted Cash [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	6,825
Other assets
Business Acquisition [Line Items]
Business Acquisition, PPA, Assets Acquired	87,713
Debt [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	1,759,550
Interest Rate Cash Flow Hedge Liability at Fair Value [Domain]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	14,961
Other Liabilities [Member]
Business Acquisition [Line Items]
Business Acquisition, PPA, Liabilities Assumed	$ 125,034