Equity awards (Details) | 3 Months Ended |
Mar. 31, 2016USD ($)$ / sharesshares |
Stock Options Member [Member] | |
Aggregate Intrinsic Value [Abstract] | |
Outstanding, beginning of period | $ | $ 52,119,607 |
Outstanding, end of period | $ | 38,049,150 |
Exercisable, end of period | $ | $ 29,719,065 |
2006 Plan [Member] | Restricted Stock Units (RSUs) [Member] | |
Restricted stock unit award activity [Roll Forward] | |
Outstanding, beginning of period (in shares) | shares | 889,004 |
Granted (in shares) | shares | 427,592 |
Vested (in shares) | shares | (353,117) |
Forfeited (in shares) | shares | (9,599) |
Outstanding, end of period (in shares) | shares | 953,880 |
Weighted-Average Grant Price [Roll Forward] | |
Outstanding, beginning of period (in dollars per share) | $ / shares | $ 26.86 |
Granted (in dollars per share) | $ / shares | 33.83 |
Vested (in dollars per share) | $ / shares | 24.70 |
Forfeited (in dollars per share) | $ / shares | 30.06 |
Outstanding, end of period (in dollars per share) | $ / shares | $ 30.75 |
Aggregate intrinsic value [Abstract] | |
Outstanding, beginning of period | $ | $ 35,569,048 |
Outstanding, end of period | $ | $ 34,673,539 |
2006 Plan [Member] | Stock Options Member [Member] | |
Options outstanding [Roll Forward] | |
Outstanding, beginning of period (in shares) | shares | 2,964,237 |
Granted (in shares) | shares | 391,158 |
Exercised (in shares) | shares | (178,124) |
Forfeited (in shares) | shares | (12,742) |
Outstanding, end of period (in shares) | shares | 3,164,529 |
Exercisable, end of period (in shares) | shares | 1,951,044 |
Weighted-Average Exercise Price [Roll Forward] | |
Outstanding, beginning of period (in dollars per share) | $ / shares | $ 22.73 |
Granted (in dollars per share) | $ / shares | 33.83 |
Exercised (in dollars per share) | $ / shares | 18.47 |
Forfeited (in dollars per share) | $ / shares | 25.48 |
Outstanding, end of period (in dollars per share) | $ / shares | 24.33 |
Exercisable, end of period (in dollars per share) | $ / shares | $ 21.12 |
2004 Plan [Member] | Stock Options Member [Member] | |
Options outstanding [Roll Forward] | |
Outstanding, beginning of period (in shares) | shares | 29,699 |
Granted (in shares) | shares | 0 |
Exercised (in shares) | shares | (29,699) |
Forfeited (in shares) | shares | 0 |
Outstanding, end of period (in shares) | shares | 0 |
Exercisable, end of period (in shares) | shares | 0 |
Weighted-Average Exercise Price [Roll Forward] | |
Outstanding, beginning of period (in dollars per share) | $ / shares | $ 10.28 |
Granted (in dollars per share) | $ / shares | 0 |
Exercised (in dollars per share) | $ / shares | 10.28 |
Forfeited (in dollars per share) | $ / shares | 0 |
Outstanding, end of period (in dollars per share) | $ / shares | 0 |
Exercisable, end of period (in dollars per share) | $ / shares | $ 0 |