Basis of Presentation Basis of Presentation (Earnings per share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands |
3 Months Ended | |
|---|---|---|
Mar. 31, 2016 |
Mar. 31, 2015 |
|
| Numerator: | ||
| Net income | $ 83,300 | $ 54,971 |
| Less: earnings distributed to participating securities | (285) | (188) |
| Less: undistributed earnings allocated to participating securities | (404) | (166) |
| Numerator for basic earnings per share | 82,611 | 54,617 |
| Add back: undistributed earnings allocated to participating securities | 404 | 166 |
| Less: undistributed earnings reallocated to participating securities | (401) | (165) |
| Numerator for diluted earnings per share | $ 82,614 | $ 54,618 |
| Denominator: | ||
| Basic shares outstanding (shares) | 347,815 | 366,748 |
| Effect of dilutive securities (shares) | 2,662 | 3,362 |
| Diluted shares outstanding (shares) | 350,477 | 370,110 |
| Earnings Per Share [Abstract] | ||
| Earnings Per Share, Basic (usd per share) | $ 0.24 | $ 0.15 |
| Earnings Per Share, Diluted (usd per share) | $ 0.24 | $ 0.15 |