Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Earnings Per Share [Abstract]
Net earnings from continuing operations		$ 78,668	$ 85,647	$ 90,456
Less: Earnings allocated to unvested restricted stock	[1]	(999)	(1,004)	(1,067)
Net earnings allocated to common shares		$ 77,669	$ 84,643	$ 89,389
Weighted-average basic shares and unvested restricted stock outstanding (shares)		121,346	121,464	121,598
Weighted-average unvested restricted stock outstanding (shares)		(1,503)	(1,450)	(1,392)
Weighted-average basic shares outstanding (shares)		119,843	120,014	120,206
Basic net income per share (usd per share)		$ 0.65	$ 0.71	$ 0.74
Net earnings from continuing operations allocated to common shares		$ 77,669	$ 84,643	$ 89,389
Diluted net income per share (usd per share)		$ 0.65	$ 0.71	$ 0.74

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