Consolidated Statements of Changes in Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Capital	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Noncontrolling Interest [Member]
Balance, at Dec. 31, 2011	$ 363,245	$ 5,173	$ 31,801	$ 322,201		$ (375)	$ 4,445
Shares Issued, Beginning Balance at Dec. 31, 2011		5,173,000
Net income	58,010			57,230			780
Dividends paid	(57,458)			(57,458)
Unrealized net loss on available-for-sale securities	0
Deferred stock unit grant	300		300
Balance, at Sep. 30, 2012	364,097	5,173	32,101	321,973		(375)	5,225
Shares Issued, Ending Balance at Sep. 30, 2012		5,173,000
Balance, at Dec. 31, 2012	332,153	5,173	29,352	296,797	1,206	(375)	0
Shares Issued, Beginning Balance at Dec. 31, 2012	5,173,450	5,173,450
Net income	41,125			41,125			0
Dividends paid	(42,145)			(42,145)
Unrealized net loss on available-for-sale securities	(996)				(996)
Deferred stock unit grant	394		394
Other	0		(1)			1
Balance, at Sep. 30, 2013	$ 330,531	$ 5,173	$ 29,745	$ 295,777	$ 210	$ (374)	$ 0
Shares Issued, Ending Balance at Sep. 30, 2013	5,173,450	5,173,450