Stock-based Compensation - Stock Options (Details) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	May 07, 2014 shares	Mar. 31, 2018 USD ($) item $ / shares shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) $ / shares shares
Stock-based Compensation
Unrecognized compensation cost		$ 30,000
Equity Incentive Plan 2010
Stock-based Compensation
Number of shares authorized | shares		5,649,108
Shares included in the authorized shares which was previously reserved for issuance | shares		649,108
Shares
Granted (in shares) | shares	0
Employee and Directors Stock Options
Stock-based Compensation
Term of award		10 years
Vesting period		3 years
Stock-based compensation		$ 0	$ 0
Unrecognized compensation cost		$ 0
Shares
Balance at the beginning of the period (in shares) | shares		2,858,158
Exercised (in shares) | shares		(131,363)
Balance at the end of the period (in shares) | shares		2,726,795		2,858,158
Vested and exercisable at the end of the period (in shares) | shares		2,726,795
Exercise Price
Balance at the beginning of the period (in dollars per share) | $ / shares		$ 20.37
Exercised (in dollars per share) | $ / shares		20.00
Balance at the end of the period (in dollars per share) | $ / shares		20.39		$ 20.37
Vested and exercisable at the end of the period (in dollars per share) | $ / shares		$ 20.39
Remaining Contractual Term
Remaining Contractual Term (in years)		2 years 3 months		2 years 5 months 27 days
Vested and exercisable		2 years 3 months
Aggregate Intrinsic Value
Balance at the beginning of the period		$ 79,230
Exercised		3,063
Balance at the end of the period		60,624		$ 79,230
Vested and exercisable at the end of the period		$ 60,624
Restricted Stock Units
Stock-based Compensation
Number of different vesting criteria | item		4
Stock-based compensation		$ 3,400	$ 3,800
Restricted Stock Units | Vesting Tranche One
Stock-based Compensation
Vesting period		3 years
Restricted Stock Units | Vesting Tranche Three
Stock-based Compensation
Vesting period		3 years
Restricted Stock Units | Vesting Tranche Four
Stock-based Compensation
Vesting period		3 years
Restricted Stock Units | Minimum | Vesting Tranche Two
Stock-based Compensation
Vesting period		1 year
Restricted Stock Units | Maximum | Vesting Tranche Two
Stock-based Compensation
Vesting period		2 years
Restricted Stock With Total Shareholder Return Conditions | Minimum
Stock-based Compensation
Percentage of shares vested		0.00%
Restricted Stock With Total Shareholder Return Conditions | Maximum
Stock-based Compensation
Percentage of shares vested		200.00%