Segment Reporting (Narratives) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 segment	Sep. 30, 2013
Segment Reporting Information [Line Items]
Number of business segments			2
Segment Reporting Information Profit Loss
Operating expenses	$ 128,219	$ 91,625	$ 461,188	$ 247,630
Reimbursable tenant and affiliate costs	20,993	26,883	114,413	60,475
Reimbursable costs from affiliates	14,722	23,259	96,379	50,694
Stock-based compensation expense	7,979	7,852	22,979	25,430
Real Estate Ownership
Segment Reporting Information Profit Loss
Operating expenses	94,227	45,298	294,572	127,790
Investment Management
Segment Reporting Information Profit Loss
Operating expenses	33,992	46,327	166,616	119,840
Reimbursable tenant and affiliate costs	14,700	23,300	96,400	50,700
Stock-based compensation expense	7,700	7,600	22,300	24,100
CPA: 16 - Global | Real Estate Ownership
Segment Reporting Information Profit Loss
Operating expenses			$ 30,400