Earnings Per Share (Details)			3 Months Ended								6 Months Ended	12 Months Ended
	Jun. 07, 2018	Apr. 26, 2018 USD ($)	Dec. 31, 2019 $ / shares	Sep. 30, 2019 $ / shares	Jun. 30, 2019 USD ($) $ / shares	Mar. 31, 2019 $ / shares	Dec. 31, 2018 USD ($) $ / shares	Sep. 30, 2018 $ / shares	Jun. 30, 2018 USD ($) $ / shares	Mar. 31, 2018 $ / shares	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	May 11, 2018 USD ($)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share repurchase program, authorized amount					$ 50,000,000.0
Common stock repurchased and recorded as treasury stock (in shares) | shares												943,094	9,002,453
Repurchase of treasury stock												$ 13,820,000	$ 150,000,000
Net Income (Numerator)
Basic EPS - common stock												171,040,000	189,589,000	$ 139,445,000
Diluted EPS - common stock												$ 171,040,000	$ 189,589,000	$ 139,445,000
Weighted Average Shares (Denominator)
Basic EPS - common stock (in shares) | shares												126,598,564	131,716,726	135,348,938
Effect of dilutive securities:
Stock Options and Performance Units (in shares) | shares												276,756	237,466	336,031
Diluted EPS - common stock (in shares) | shares												126,875,320	131,954,192	135,684,969
Earnings Per Share
Basic EPS - common stock (in dollars per share) | $ / shares			$ 0.34	$ 0.34	$ 0.34	$ 0.34	$ 0.35	$ 0.36	$ 0.36	$ 0.38		$ 1.35	$ 1.44	$ 1.03
Diluted EPS - common stock (in dollars per share) | $ / shares			$ 0.34	$ 0.34	$ 0.34	$ 0.34	$ 0.35	$ 0.36	$ 0.36	$ 0.38		$ 1.35	$ 1.44	$ 1.03
Stock options and restricted shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares of common stock | shares												894,000	617,000
Convertible Notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Aggregate principal amount issued							$ 217,500,000		$ 217,500,000		$ 217,500,000		$ 217,500,000		$ 200,000,000
Initial conversion rate	0.0450760											0.0450760
Repurchase of treasury stock		$ 76,000,000.0									24,000,000.0
Share Repurchase Program 1
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share repurchase program, authorized amount					$ 50,000,000		100,000,000.0				100,000,000.0		100,000,000.0
Share Repurchase Program 2
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Share repurchase program, authorized amount							$ 50,000,000.0				$ 50,000,000.0		$ 50,000,000.0