Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings per share — Basic:
Earnings from continuing operations	$ 58,913	$ 85,138	$ 148,535	$ 215,365
Less: Earnings allocated to unvested stock	(222)	(261)	(536)	(674)
Earnings from continuing operations available to common shareholders — Basic	$ 58,691	$ 84,877	$ 147,999	$ 214,691
Weighted average common shares outstanding - Basic (in shares)	52,405	52,953	52,671	53,029
Earnings from continuing operations per common share — Basic (in dollars per share)	$ 1.12	$ 1.60	$ 2.81	$ 4.05
Earnings per share — Diluted:
Earnings from continuing operations	$ 58,913	$ 85,138	$ 148,535	$ 215,365
Less: Earnings allocated to unvested stock	(222)	(260)	(536)	(672)
Earnings from continuing operations available to common shareholders — Diluted	$ 58,691	$ 84,878	$ 147,999	$ 214,693
Weighted average common shares outstanding - Basic (in shares)	52,405	52,953	52,671	53,029
Effect of dilutive equity awards (in shares)	371	338	356	315
Weighted average common shares outstanding — Diluted (shares)	52,776	53,291	53,027	53,344
Earnings from continuing operations per common share — Diluted (in dollars per share)	$ 1.11	$ 1.59	$ 2.79	$ 4.02
Anti-dilutive equity awards not included above (in shares)	843	653	889	836