Real Estate Investments (Assets Acquired and Liabilities Assumed) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
2015 Acquisitions [Member]
Assets Acquired and Liabilities Assumed
Land	$ 5,051
Buildings, fixtures and improvements	26,503
Land and construction in progress	2,140
Total tangible assets	33,694
In-place leases	2,580
Above-market leases	153
Below-market leases	(108)
Fair value adjustment of assumed notes payable	0
Total purchase price of assets acquired	36,319
Mortgage notes payable assumed	0
Cash paid for acquired real estate investments	$ 36,319
2014 Acquisitions, Excluding Cole Merger, ARCT IV Merger And CCPT Merger [Member]
Assets Acquired and Liabilities Assumed
Land		$ 808,930
Buildings, fixtures and improvements		2,494,379
Land and construction in progress		11,030
Total tangible assets		3,314,339
In-place leases		545,389
Above-market leases		112,484
Below-market leases		(107,185)
Fair value adjustment of assumed notes payable		(23,589)
Total purchase price of assets acquired		3,841,438
Mortgage notes payable assumed		(301,532)
Cash paid for acquired real estate investments		$ 3,539,906
2013 Acquisitions, Excluding Caplease Merger [Member]
Assets Acquired and Liabilities Assumed
Land			$ 883,491
Buildings, fixtures and improvements			2,311,211
Land and construction in progress			0
Total tangible assets			3,194,702
In-place leases			334,839
Above-market leases			12,317
Below-market leases			(21,446)
Fair value adjustment of assumed notes payable			0
Total purchase price of assets acquired			3,520,412
Mortgage notes payable assumed			0
Cash paid for acquired real estate investments			$ 3,520,412