Basis of Presentation Basis of Presentation (Earnings per share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2016 |
Jun. 30, 2015 |
Jun. 30, 2016 |
Jun. 30, 2015 |
|
| Numerator: | ||||
| Net income | $ 117,760 | $ 103,324 | $ 201,060 | $ 158,295 |
| Less: earnings distributed to participating securities | (283) | (185) | (568) | (373) |
| Less: undistributed earnings allocated to participating securities | (791) | (475) | (1,064) | (647) |
| Numerator for basic earnings per share | 116,686 | 102,664 | 199,428 | 157,275 |
| Add back: undistributed earnings allocated to participating securities | 791 | 475 | 1,064 | 647 |
| Less: undistributed earnings reallocated to participating securities | (785) | (471) | (1,055) | (641) |
| Numerator for diluted earnings per share | $ 116,692 | $ 102,668 | $ 199,437 | $ 157,281 |
| Denominator: | ||||
| Basic shares outstanding (shares) | 345,240 | 361,009 | 346,528 | 363,863 |
| Effect of dilutive securities (shares) | 2,759 | 3,232 | 2,710 | 3,297 |
| Diluted shares outstanding (shares) | 347,999 | 364,241 | 349,238 | 367,160 |
| Earnings Per Share [Abstract] | ||||
| Earnings Per Share, Basic (usd per share) | $ 0.34 | $ 0.28 | $ 0.58 | $ 0.43 |
| Earnings Per Share, Diluted (usd per share) | $ 0.34 | $ 0.28 | $ 0.57 | $ 0.43 |