Consolidated Statement Of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Cumulative Dividends In Excess Of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Parent [Member]	Noncontrolling Interest [Member]
Balance, value at Dec. 31, 2010	$ 442,500	$ 277	$ 462,392	$ (35,499)	$ 15,330	$ 442,500	$ 0
Balance, shares at Dec. 31, 2010		27,689,392
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to common stockholders	81,132			81,132	(8,149)	72,983	0
Comprehensive income	72,983
Shares issued on stock options exercised, shares		61,816
Shares issued on stock options exercised, value	(200)	(1)	(199)			(200)
Share-based Compensation			3,087
Share-based compensation	3,087					3,087
Dividends declared, $1.43 per share	(75,285)			(75,285)		(75,285)
Balance, value at Dec. 31, 2011	443,485	278	465,678	(29,652)	7,181	443,485	0
Balance, shares at Dec. 31, 2011		27,751,208
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to common stockholders	90,731			90,731	374	91,105	167
Comprehensive income	91,272
Noncontrolling Interest, Increase from Subsidiary Equity Issuance	10,964						10,964
Distributions to noncontrolling interest	(266)						(266)
Shares issued on stock options exercised, shares		106,009
Shares issued on stock options exercised, value	(2)	(1)	(3)			(2)
Share-based Compensation			2,168
Share-based compensation	2,168					2,168
Dividends declared, $1.43 per share	(79,574)			(79,574)		(79,574)
Balance, value at Dec. 31, 2012	468,047
Balance, shares at Dec. 31, 2012	27,857,217
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to common stockholders	106,183			106,183	1,983	108,166	999
Comprehensive income	109,165
Distributions to noncontrolling interest	(1,250)						(1,250)
Stock Issued During Period, Shares, New Issues	5,175,000	5,175,000
Stock Issued During Period, Value, New Issues	282,541	51	282,490			282,541
Shares issued on stock options exercised, shares		18,959
Shares issued on stock options exercised, value	(146)	0	(146)			(146)
Share-based Compensation			2,339
Share-based compensation	2,339					2,339
Assignment of net assets in equity-method investee	817		817			817
Dividends declared, $1.43 per share	(84,645)			(84,645)		(84,645)
Balance, value at Dec. 31, 2013	$ 777,160	$ 330	$ 753,635	$ 3,043	$ 9,538	$ 766,546	$ 10,614
Balance, shares at Dec. 31, 2013	33,051,176	33,051,176