Consolidated Statement Of Equity - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Cumulative Dividends In Excess Of Net Income [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, shares at Dec. 31, 2016	39,847,860	39,847,860
Balance, value at Dec. 31, 2016	$ 1,209,590	$ 398	$ 1,173,588	$ 29,873	$ 5,731
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	44,230			44,230	(8,810)
Comprehensive income	35,420
Stock Issued During Period, Shares, New Issues		1,123,184
Stock Issued During Period, Value, New Issues	79,797	$ 12	79,785
Shares issued on stock options exercised, shares		7,890
Adjustments Related to Tax Withholding for Share-based Compensation	(116)		(116)
Share-based compensation	1,523		1,523
Dividends declared, $1.54 per share	$ (38,930)			(38,930)
Balance, shares at Mar. 31, 2017	40,978,934	40,978,934
Balance, value at Mar. 31, 2017	$ 1,287,284	$ 410	$ 1,254,780	$ 35,173	$ (3,079)