Stock-based Compensation - Stock Options (Details) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) item $ / shares shares	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($) $ / shares shares
Stock-based Compensation
Unrecognized compensation cost	$ 21,600		$ 21,600
Equity Incentive Plan 2010
Stock-based Compensation
Number of shares authorized | shares	5,769,256		5,769,256
Shares included in the authorized shares which was previously reserved for issuance | shares	769,256		769,256
Employee and Directors Stock Options
Stock-based Compensation
Term of award			10 years
Vesting period			3 years
Stock-based compensation	$ 0	$ 0	$ 0	$ 0
Unrecognized compensation cost	$ 0		$ 0
Shares
Balance at the beginning of the period (in shares) | shares			3,308,158
Exercised (in shares) | shares			(97,500)
Balance at the end of the period (in shares) | shares	3,210,658		3,210,658		3,308,158
Vested and exercisable at the end of the period (in shares) | shares	3,210,658		3,210,658
Exercise Price
Balance at the beginning of the period (in dollars per share) | $ / shares			$ 20.40
Exercised (in dollars per share) | $ / shares			22.71
Balance at the end of the period (in dollars per share) | $ / shares	$ 20.33		20.33		$ 20.40
Vested and exercisable at the end of the period (in dollars per share) | $ / shares	$ 20.33		$ 20.33
Remaining Contractual Term
Remaining Contractual Term (in years)			2 years 8 months 27 days		3 years 6 months
Vested and exercisable			2 years 8 months 27 days
Aggregate Intrinsic Value
Balance at the beginning of the period			$ 46,086
Exercised			1,618
Balance at the end of the period	$ 71,569		71,569		$ 46,086
Vested and exercisable at the end of the period	71,569		$ 71,569
Restricted Stock Units
Stock-based Compensation
Number of different vesting criteria | item			4
Stock-based compensation	$ 5,400	$ 4,600	$ 14,400	$ 12,300
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%