Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						6 Months Ended
	Jun. 30, 2018		Mar. 31, 2018		Jun. 30, 2017		Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 115,735		$ 118,276		$ 93,647		$ 234,011	$ 172,315
Less: Earnings allocated to unvested restricted stock	(1,348)	[1]	(1,115)	[1]	(1,080)	[1]	(2,469)	(2,082)
Net earnings allocated to common shares	$ 114,387		$ 117,161		$ 92,567		$ 231,542	$ 170,233
Weighted-average basic shares and unvested restricted stock outstanding (shares)	126,082		127,487		121,422		126,780	121,384
Weighted-average unvested restricted stock outstanding (shares)	(1,466)		(1,413)		(1,455)		(1,439)	(1,479)
Weighted-average basic shares outstanding (shares)	124,616		126,074		119,967		125,341	119,905
Basic net income per share (usd per share)	$ 0.92		$ 0.93		$ 0.77		$ 1.85	$ 1.42
Net earnings from continuing operations allocated to common shares	$ 114,387		$ 117,161		$ 92,567		$ 231,542	$ 170,233
Diluted net income per share (usd per share)	$ 0.92		$ 0.93		$ 0.77		$ 1.85	$ 1.42

[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.