Consolidated Statement Of Equity - 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]	Parent [Member]
Balance, shares at Dec. 31, 2017		41,532,154
Balance, value at Dec. 31, 2017		$ 415	$ 1,289,919	$ 32,605	$ (822)	$ 1,322,117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders	$ 38,432			38,432	1,922	40,354
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	$ 40,354
Payments of Stock Issuance Costs			(56)			(56)
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments			(2,427)			(2,427)
Stock Issued During Period, Value, New Issues						1,425
Share-based compensation			1,425
Dividends declared, $1.54 per share				(41,532)		(41,532)
Balance, value at Mar. 31, 2018		$ 415	$ 1,288,861	29,270	1,335	$ 1,319,881
Balance, shares at Mar. 31, 2018		41,532,154
Balance, shares at Dec. 31, 2018	42,700,411
Balance, value at Dec. 31, 2018	$ 1,389,713
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders	35,679
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	34,722
Balance, value at Mar. 31, 2019	$ 1,415,984
Balance, shares at Mar. 31, 2019	43,199,318
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ (235)	$ 235