Schedule III - Real Estate and Accumulated Depreciation (Real Estate and Accumulated Depreciation Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance, beginning of period	$ 1,511,647	$ 1,345,439	$ 1,210,289
Disposal of fixed assets	(124,684)	(75,770)	(37,443)
New acquisition of properties	257,683	178,864	138,050
Improvements	106,873	63,114	34,543
Balance, end of period	1,751,519	1,511,647	1,345,439
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of period	371,730	358,605	335,289
Disposal of fixed assets	(40,844)	(37,531)	(22,643)
Depreciation for period	55,955	50,656	45,959
Balance, end of period	$ 386,841	$ 371,730	$ 358,605