Equity - Change in ownership of less-than-wholly-owned subsidiary (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Noncontrolling Interest [Line Items]
Net income	$ 4,153	$ 19,783	$ 14,127	$ (5,473)
Net transfers to the noncontrolling interest			(8,189)
Change to the Company's total stockholders' equity from net income attributable to common stockholders and transfers to noncontrolling interest			7,237
Cumulative Net Income Attributable to Common Stockholders [Member]
Noncontrolling Interest [Line Items]
Net income			13,814
Net transfers to the noncontrolling interest
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Net income
Net decrease in the Company's additional paid-in capital for purchase of subsidiary partnership interest			(6,577)
Net transfers to the noncontrolling interest			$ (6,577)