Consolidated Statement Of Equity - USD ($)	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]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,322,117,000	$ 415,000	$ 1,289,919,000	$ 32,605,000	$ (822,000)	$ 1,322,117,000	$ 0
Balance, shares at Dec. 31, 2017		41,532,154
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders				38,432,000	1,922,000	40,354,000
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest							0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	40,354,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt, Subsequent Adjustments	(2,427,000)		(2,427,000)			(2,427,000)	0
Payments of Stock Issuance Costs	(56,000)		56,000			56,000	0
Share-based compensation	1,425,000		1,425,000			1,425,000	0
Dividends declared, $1.54 per share	(41,532,000)			(41,532,000)		(41,532,000)	0
Balance, shares at Dec. 31, 2017		41,532,154
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders	76,271,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	78,996,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	78,996,000
Balance, shares at Jun. 30, 2018		42,171,866
Cumulative Effect of New Accounting Principle in Period of Adoption				(235,000)	235,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders	37,839,000			37,839,000	803,000	38,642,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	38,642,000
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest							0
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 38,642,000
Stock Issued During Period, Shares, New Issues	628,403
Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture	11,309
Stock Issued During Period, Value, New Issues	$ 44,976,000	$ 7,000	44,969,000			44,976,000	0
Share-based Payment Arrangement, Decrease for Tax Withholding Obligation	(325,000)		325,000			325,000	0
Share-based compensation	369,000		369,000			369,000	0
Dividends declared, $1.54 per share	(42,171,000)			(42,171,000)		(42,171,000)	0
Balance, shares at Jun. 30, 2018		42,171,866
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	1,361,372,000	$ 422,000	1,333,874,000	24,938,000	2,138,000	1,361,372,000	0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,389,713,000	$ 427,000	1,369,919,000	18,068,000	1,299,000	1,389,713,000	0
Balance, shares at Dec. 31, 2018	42,700,411	42,700,411
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to common stockholders	$ 75,658,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	70,900,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 70,899,000
Balance, shares at Jun. 30, 2019	43,357,018	43,357,018
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	$ 1,419,686,000	$ 434,000	$ 1,419,228,000	$ 2,842,000	$ (3,459,000)	$ 1,419,045,000	$ 641,000