Consolidated Statements of Changes in Shareholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings (Deficit)	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2016	$ 1,834,314	$ 786	$ 1,521,190	$ 315,890	$ (3,552)
Beginning Balance (in shares) at Dec. 31, 2016		78,593,133
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares to stockholders, directors and employees	0	$ 3	(3)
Issuance of common shares to stockholders, directors and employees (in shares)		344,017
Repurchase of common shares from stockholders, directors and employees	(4,862)	$ (2)	(4,860)
Repurchase of common shares from stockholders', directors and employees (in shares)		(229,187)
Amortization of share-based payments	11,469		11,469
Dividends declared	(83,433)			(83,433)
Net income	147,874			147,874
Net derivative loss reclassified into earnings	2,202				2,202
Beginning Balance (in shares) at Dec. 31, 2017		78,707,963
Beginning Balance at Dec. 31, 2017	1,907,564	$ 787	1,527,796	380,331	(1,350)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common shares to stockholders, directors and employees	0	$ 4	(4)
Issuance of common shares to stockholders, directors and employees (in shares)		423,202
Repurchase of common shares from stockholders, directors and employees	(71,421)	$ (37)	(71,384)
Repurchase of common shares from stockholders', directors and employees (in shares)		(3,676,654)
Amortization of share-based payments	10,523		10,523
Reclassification of prior year director stock award liability			1,848
Dividends declared	(88,730)			(88,730)
Net income	247,919			247,919
Net derivative loss reclassified into earnings	$ 1,166				1,166
Beginning Balance (in shares) at Dec. 31, 2018	75,454,511	75,454,511
Beginning Balance at Dec. 31, 2018	$ 2,008,681	$ 754	1,468,779	539,332	(184)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption				(188)
Issuance of common shares to stockholders, directors and employees	0	$ 13	(13)
Issuance of common shares to stockholders, directors and employees (in shares)		1,281,598
Repurchase of common shares from stockholders, directors and employees	(36,739)	$ (16)	(36,723)
Repurchase of common shares from stockholders', directors and employees (in shares)		(1,613,980)
Amortization of share-based payments	13,825		13,825
Reclassification of prior year director stock award liability			796
Dividends declared	(91,328)			(91,328)
Net income	156,575			156,575
Net derivative loss reclassified into earnings	$ 184				(184)
Beginning Balance (in shares) at Dec. 31, 2019	74,991,025	75,122,129
Beginning Balance at Dec. 31, 2019	$ 2,052,684	$ 751	$ 1,446,664	605,269	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption				$ 690