Summary of Significant Accounting Policies - Deferred Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred costs and other assets
Deferred lease costs, net	$ 250,261	$ 240,229
In-place lease intangibles, net	153,015	188,219
Acquired above market lease intangibles, net	112,024	67,363
Marketable securities of our captive insurance companies	58,142	87,257
Goodwill	20,098	20,098
Other marketable and non-marketable securities	308,591	278,026
Prepaids, notes receivable and other assets, net	451,457	385,576
Deferred costs and other assets	1,353,588	1,266,768
Deferred Lease Costs
Deferred lease costs, gross	464,226	429,985
Accumulated amortization	(213,965)	(189,756)
Deferred lease costs, net	250,261	240,229
Amortization, included in statements of operations and comprehensive income
Amortization of deferred leasing costs	$ 49,993	$ 43,788	$ 39,488