Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings per share — Basic:
Earnings from continuing operations	$ 83,967	$ 73,875	$ 208,759	$ 177,252
Less: Distributed and undistributed earnings allocated to nonvested stock	(275)	(643)	(879)	(1,636)
Earnings from continuing operations available to common shareholders — Basic	83,692	73,232	207,880	175,616
Weighted average common shares outstanding - Basic (shares)	52,459	51,788	52,559	51,397
Earnings from continuing operations per common share - Basic (in dollars per share)	$ 1.60	$ 1.41	$ 3.96	$ 3.42
Earnings per share — Diluted:
Earnings from continuing operations	83,967	73,875	208,759	177,252
Less: Distributed and undistributed earnings allocated to nonvested stock	(273)	(639)	(873)	(1,625)
Earnings from continuing operations available to common shareholders — Diluted	$ 83,694	$ 73,236	$ 207,886	$ 175,627
Weighted average common shares outstanding - Basic (shares)	52,459	51,788	52,559	51,397
Effect of dilutive equity awards (shares)	515	440	487	451
Weighted average common shares outstanding - Diluted (shares)	52,974	52,228	53,046	51,848
Earnings from continuing operations per common share - Diluted (in dollars per share)	$ 1.58	$ 1.40	$ 3.92	$ 3.39
Anti-dilutive equity awards not included above (shares)	8	584	212	863