Schedule III - Real Estate and Accumulated Depreciation Reconciliation of Accumulated Depreciation (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
SEC Schedule III, Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance, beginning of year	$ 295,351	$ 257,091	$ 224,019
Depreciation expense	89,505	49,947	35,302
Disposals	(7,304)	(11,687)	(2,230)
Balance, end of year	$ 377,552	$ 295,351	$ 257,091