Consolidated Statement Of Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Capital In Excess Of Par Value [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, 2012	$ 468,047	$ 279	$ 467,843	$ (18,495)	$ 7,555	$ 457,182	$ 10,865
Balance, shares at Dec. 31, 2012		27,857,217
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributable to common stockholders	35,663			35,663	2,427	38,090	358
Comprehensive income	38,448
Distributions to noncontrolling interest	(441)						(441)
Shares issued on stock options exercised, shares		18,959
Shares issued on stock options exercised, value	146	0	146			146
Share-based Compensation			1,833
Share-based compensation	1,833					1,833
Assignment of net assets in equity-method investee	817		817
Dividends declared, $1.43 per share	(39,863)			(39,863)		(39,863)
Balance, value at Jun. 30, 2013	$ 468,987	$ 279	$ 470,639	$ (22,695)	$ 9,982	$ 458,205	$ 10,782
Balance, shares at Jun. 30, 2013	27,876,176	27,876,176