Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2018		Jun. 30, 2018		Sep. 30, 2017		Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 116,287		$ 115,735		$ 101,466		$ 350,298	$ 273,781
Less: Earnings allocated to unvested restricted stock	(1,428)	[1]	(1,348)	[1]	(1,149)	[1]	(3,899)	(3,239)
Net earnings allocated to common shares	$ 114,859		$ 114,387		$ 100,317		$ 346,399	$ 270,542
Weighted-average basic shares and unvested restricted stock outstanding (shares)	123,657		126,082		121,447		125,728	121,405
Weighted-average unvested restricted stock outstanding (shares)	(1,537)		(1,466)		(1,394)		(1,473)	(1,450)
Weighted-average basic shares outstanding (shares)	122,120		124,616		120,053		124,255	119,955
Basic net income per share (usd per share)	$ 0.94		$ 0.92		$ 0.84		$ 2.79	$ 2.26
Net earnings from continuing operations allocated to common shares	$ 114,859		$ 114,387		$ 100,317		$ 346,399	$ 270,542
Diluted net income per share (usd per share)	$ 0.94		$ 0.92		$ 0.84		$ 2.79	$ 2.26

[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.