Condensed Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total USD ($)	Common Class A [Member]	Common Class B [Member]	Total Stockholders' Equity [Member] USD ($)	Common Stock [Member] Common Class A [Member] USD ($)	Common Stock [Member] Common Class B [Member] USD ($)	Additional Paid-in Capital [Member] USD ($)	Retained Earnings [Member] USD ($)	Noncontrolling Interest [Member] USD ($)
Beginning balance at Dec. 31, 2013	$ 1,003,185			$ 385,158	$ 945	$ 11	$ 316,558	$ 67,644	$ 618,027
Ending balance (in shares) at Dec. 31, 2013		94,484,023	1,122,130		94,484,000	1,122,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	36,512			14,203				14,203	22,309
Equity compensation:
LTIP units	1,670								1,670
Restricted stock					2,000
Restricted stock	300			300			300
Dividends and distributions	(41,823)			(16,251)				(16,251)	(25,572)
Ending balance at Jun. 30, 2014	$ 999,844			$ 383,410	$ 945	$ 11	$ 316,858	$ 65,596	$ 616,434
Beginning balance balance (in shares) at Jun. 30, 2014		84,486,204	1,121,786		94,486,000	1,122,000