Secured and unsecured senior debt Interest expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Interest expense incurred
Gross interest	$ 126,404	$ 128,567		$ 131,935
Capitalized interest	(47,105)	(60,615)		(62,751)
Interest expense	$ 79,299	$ 67,952	[1]	$ 69,184	[1]

[1] Includes interest expense related to and classified in income from discontinued operations in the accompanying consolidated statements of income.