Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Earnings Per Share [Abstract]
Net earnings from continuing operations		$ 118,276	$ 84,037	$ 78,668
Less: Earnings allocated to unvested restricted stock	[1]	(1,115)	(951)	(999)
Net earnings allocated to common shares		$ 117,161	$ 83,086	$ 77,669
Weighted-average basic shares and unvested restricted stock outstanding (shares)		127,487	127,971	121,346
Weighted-average unvested restricted stock outstanding (shares)		(1,413)	(1,440)	(1,503)
Weighted-average basic shares outstanding (shares)		126,074	126,531	119,843
Basic net income per share (usd per share)		$ 0.93	$ 0.66	$ 0.65
Net earnings from continuing operations allocated to common shares		$ 117,161	$ 83,086	$ 77,669
Diluted net income per share (usd per share)		$ 0.93	$ 0.66	$ 0.65

[1] Represents cash dividends paid to holders of unvested restricted stock, net of forfeitures, plus undistributed earnings amounts available to holders of unvested restricted stock, if any.