Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net earnings from continuing operations	$ 93,647	$ 78,668	$ 82,168	$ 172,315	$ 172,624
Less: Earnings allocated to unvested restricted stock	(1,080)	(999)	(863)	(2,082)	(1,933)
Net earnings allocated to common shares	$ 92,567	$ 77,669	$ 81,305	$ 170,233	$ 170,691
Weighted-average basic shares and unvested restricted stock outstanding (shares)	121,422	121,346	121,799	121,384	121,698
Weighted-average unvested restricted stock outstanding (shares)	(1,455)	(1,503)	(1,481)	(1,479)	(1,436)
Weighted-average basic shares outstanding (shares)	119,967	119,843	120,318	119,905	120,262
Basic net income per share (usd per share)	$ 0.77	$ 0.65	$ 0.68	$ 1.42	$ 1.42
Net earnings from continuing operations allocated to common shares	$ 92,567	$ 77,669	$ 81,305	$ 170,233	$ 170,691
Diluted net income per share (usd per share)	$ 0.77	$ 0.65	$ 0.68	$ 1.42	$ 1.42