Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings per share — Basic:
Earnings from continuing operations	$ 85,138	$ 90,811	$ 215,365	$ 230,054
Less: Earnings allocated to unvested stock	(261)	(266)	(674)	(654)
Earnings from continuing operations available to common shareholders — Basic	$ 84,877	$ 90,545	$ 214,691	$ 229,400
Weighted average common shares outstanding - Basic (shares)	52,953	52,888	53,029	52,770
Earnings from continuing operations per common share — Basic (in dollars per share)	$ 1.60	$ 1.71	$ 4.05	$ 4.35
Earnings per share — Diluted:
Earnings from continuing operations	$ 85,138	$ 90,811	$ 215,365	$ 230,054
Less: Earnings allocated to unvested stock	(260)	(265)	(672)	(649)
Earnings from continuing operations available to common shareholders — Diluted	$ 84,878	$ 90,546	$ 214,693	$ 229,405
Weighted average common shares outstanding - Basic (shares)	52,953	52,888	53,029	52,770
Effect of dilutive equity awards (shares)	338	445	315	476
Weighted average common shares outstanding — Diluted (shares)	53,291	53,333	53,344	53,246
Earnings from continuing operations per common share — Diluted (in dollars per share)	$ 1.59	$ 1.70	$ 4.02	$ 4.31
Anti-dilutive equity awards not included above (shares)	653	352	836	300