Stockholders' Equity - Change in Ownership of Less-than-wholly-owned Subsidiary (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Noncontrolling Interest [Line Items]
Net income attributable to common stockholders	$ 52,437	$ 11,834	$ 12,145	$ 9,156	$ 18,658	$ 27,480	$ 17,916	$ 5,382	$ 85,571	$ 69,436	$ 32,200
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									85,571	69,436	25,310
Cumulative net income attributable to common stockholders [Member]
Noncontrolling Interest [Line Items]
Net income attributable to common stockholders									85,571	$ 69,436	31,887
Net transfers to the noncontrolling interest												0
Additional Paid-in Capital [Member]
Noncontrolling Interest [Line Items]
Net decrease in the Company's additional paid-in capital for purchase of subsidiary partnership interest									$ 0		(6,577)
Net transfers to the noncontrolling interest											$ (6,577)	$ (6,577)