Employee Benefits and Share-Based Compensation - Restricted Stock Activity (Details) - 2009 Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restricted Stock Units (RSUs)
Number of Shares
Outstanding and unvested December 31	417
Granted (Awarded)	289
Vested (Released)	(179)
Forfeited	(22)
Outstanding and unvested at December 31	505	417
Weighted-Average Grant Date Fair Value
Outstanding and unvested December 31	$ 28.49
Granted (Awarded)	32.58	$ 31.44	$ 28.88
Vested (Released)	26.83
Forfeited	28.37
Outstanding and unvested at December 31	$ 31.42	$ 28.49
Weighted-Average Remaining Years	1 year 7 months 5 days	1 year 7 months
Aggregate Intrinsic Value
Non-vested at December 31, 2016	$ 17,135
Fair value of restricted stock units	4,800	$ 4,700	$ 3,200
Unrecognized compensation cost	$ 12,800	$ 11,200
Weighted average period of compensation cost recognized	2 years 10 months 17 days	2 years 10 months 15 days
Restricted Stock
Number of Shares
Outstanding and unvested December 31	31
Granted (Awarded)	34
Vested (Released)	(35)
Outstanding and unvested at December 31	30	31
Weighted-Average Grant Date Fair Value
Outstanding and unvested December 31	$ 35.97
Granted (Awarded)	31.59	$ 36.05	$ 26.42
Vested (Released)	35.45
Forfeited	0.00
Outstanding and unvested at December 31	$ 31.57	$ 35.97
Aggregate Intrinsic Value
Fair value of restricted stock units	$ 1,200	$ 1,100	$ 1,000
Unrecognized compensation cost	$ 400
Weighted average period of compensation cost recognized	4 months 15 days	4 months 15 days