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	11,231			4,369				4,369	6,862
Equity compensation:
LTIP units	900								900
Restricted stock (in shares)					13,000
Restricted stock	125			125			125
Dividends and distributions	(20,901)			(8,128)				(8,128)	(12,773)
Ending balance at Mar. 31, 2014	$ 994,540			$ 381,524	$ 945	$ 11	$ 316,683	$ 63,885	$ 613,016
Beginning balance balance (in shares) at Mar. 31, 2014		94,496,534	1,122,130		94,497,000	1,122,000