Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings per share — Basic:
Earnings from continuing operations	$ 90,811	$ 83,895	$ 230,054	$ 208,742
Less: Distributed and undistributed earnings allocated to nonvested stock	(266)	(275)	(654)	(879)
Earnings from continuing operations available to common shareholders — Basic	$ 90,545	$ 83,620	$ 229,400	$ 207,863
Weighted average common shares outstanding - Basic (shares)	52,888	52,459	52,770	52,559
Earnings from continuing operations per common share — Basic	$ 1.71	$ 1.60	$ 4.35	$ 3.96	[1]
Earnings per share — Diluted:
Earnings from continuing operations	$ 90,811	$ 83,895	$ 230,054	$ 208,742
Less: Distributed and undistributed earnings allocated to nonvested stock	(265)	(273)	(649)	(873)
Earnings from continuing operations available to common shareholders — Diluted	$ 90,546	$ 83,622	$ 229,405	$ 207,869
Weighted average common shares outstanding - Basic (shares)	52,888	52,459	52,770	52,559
Effect of dilutive equity awards (shares)	445	515	476	487
Weighted average common shares outstanding — Diluted (shares)	53,333	52,974	53,246	53,046
Earnings from continuing operations per common share — Diluted	$ 1.70	$ 1.58	$ 4.31	$ 3.92	[1]
Anti-dilutive equity awards not included above (shares)	352	8	300	212

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