Consolidated Statements of Shareholder's Equity Statement - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Common Stock, Shares, Outstanding		78,707,963
Stockholders' Equity Attributable to Parent	$ 1,907,564	$ 787	$ 1,527,796	$ 380,331	$ (1,350)
Stock Issued During Period, Shares, New Issues		293,680
Stock Issued During Period, Value, New Issues	0	$ 3	(3)
Stock Repurchased During Period, Shares		(462,452)
Stock Repurchased During Period, Value	(9,413)	$ 5	9,408
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,048		2,048
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition			1,680
Dividends, Common Stock, Cash	(22,085)			22,085
Net income	57,547			57,547
Net derivative loss reclassified into earnings	301				(301)
Net income	107,750
Net derivative loss reclassified into earnings	595
Common Stock, Shares, Outstanding		78,539,191
Stockholders' Equity Attributable to Parent	1,937,454	$ 785	1,522,113	415,605	(1,049)
Cumulative Effect of New Accounting Principle in Period of Adoption				(188)
Stock Repurchased During Period, Shares		295,153
Stock Repurchased During Period, Value	(5,574)	$ (3)	(5,571)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,750		2,750
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition			187
Dividends, Common Stock, Cash	(21,908)			(21,908)
Net income	50,203			50,203
Net derivative loss reclassified into earnings	294				(294)
Common Stock, Shares, Outstanding		78,244,038
Stockholders' Equity Attributable to Parent	$ 1,963,406	$ 782	1,519,479	443,900	(755)
Common Stock, Shares, Outstanding	75,324,989	75,454,511
Stockholders' Equity Attributable to Parent	$ 2,008,681	$ 754	1,468,779	539,332	(184)
Stock Issued During Period, Shares, New Issues		276,923
Stock Issued During Period, Value, New Issues	0	$ 3	(3)
Stock Repurchased During Period, Shares		(653,796)
Stock Repurchased During Period, Value	(11,424)	$ 6	11,418
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,410		2,410
APIC, Share-based Payment Arrangement, Restricted Stock Unit, Increase for Cost Recognition			796
Dividends, Common Stock, Cash	(22,518)			(22,518)
Net income	34,810			34,810
Net derivative loss reclassified into earnings	184				(184)
Net income	65,922
Net derivative loss reclassified into earnings	184
Common Stock, Shares, Outstanding		75,077,638
Stockholders' Equity Attributable to Parent	2,012,939	$ 751	1,460,564	551,624	0
Stock Issued During Period, Shares, New Issues		35,000
Stock Issued During Period, Value, New Issues	0	$ 0	0
Stock Repurchased During Period, Shares		129,524
Stock Repurchased During Period, Value	(2,864)	$ (1)	(2,863)
APIC, Share-based Payment Arrangement, Increase for Cost Recognition	2,833		2,833
Dividends, Common Stock, Cash	(22,536)			(22,536)
Net income	31,112			31,112
Net derivative loss reclassified into earnings	$ 0
Common Stock, Shares, Outstanding	74,983,114	74,983,114
Stockholders' Equity Attributable to Parent	$ 2,021,484	$ 750	$ 1,460,534	$ 560,200	$ 0