Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - EPS and New Accounting Principle (Details)

v3.10.0.1
Summary of Significant Accounting Policies - EPS and New Accounting Principle (Details) - USD ($)
shares in Thousands, $ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Earnings per share        
Basic weighted average number of shares outstanding 316,992 315,401 316,733 315,179
Diluted weighted average number of shares outstanding 316,992 315,401 316,733 315,927
U.S. Statutory federal income tax rate (as a percent) 21.00% 35.00% 21.00% 35.00%
Benefit recognized from reduction in deferred tax liabilities due to a change in state tax laws $ 20,000   $ 20,000  
Employee tax withholding for settlement of equity compensation awards     $ (7,967) $ (8,433)
Restricted stock and restricted stock unit        
Earnings per share        
Add: Dilutive effect of non-vested restricted stock units       710
Weighted Average Anti-dilutive Awards 2,899 5,105 3,088 1,596
Stock options        
Earnings per share        
Weighted Average Anti-dilutive Awards 639 679 646 681
Performance share unit awards        
Earnings per share        
Add: Dilutive effect of non-vested restricted stock units       38
Weighted Average Anti-dilutive Awards 1,860 1,213 1,556 896