Summary of Restricted Stock Unit Activity (Details) - Restricted Stock Units - $ / shares shares in Thousands |
1 Months Ended | 6 Months Ended | 12 Months Ended |
|---|---|---|---|
Jan. 31, 2015 |
Jun. 30, 2015 |
Dec. 31, 2012 |
|
| Share Based Compensation Arrangement By Share Based Payment Award [Line Items] | |||
| Non-vested total at January 1, 2015 | 516 | 516 | |
| Granted | 93 | 150 | 158 |
| Performance share adjustment | 93 | ||
| Vested | (302) | ||
| Forfeited | (19) | ||
| Non-vested total at June 30, 2015 | 438 | ||
| Weighted-average grant date fair value (per share), non-vested total beginning balance | $ 41.46 | $ 41.46 | |
| Weighted-average grant date fair value (per share), granted | 55.63 | ||
| Weighted-average grant date fair value (per share), Performance share adjustment | 38.11 | ||
| Weighted-average grant date fair value (per share), vested | 39.40 | ||
| Weighted-average grant date fair value (per share), forfeited | 44.80 | ||
| Weighted-average grant date fair value (per share), non-vested total ending balance | $ 46.88 |