Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (Stock Options Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	694,881
Exercised (in shares)	(329,502)
Canceled (in shares)	(8,993)
Outstanding at December 31 (in shares)	356,386	694,881
Vested and Expected to Vest at December 31(in shares)	356,386
Exercisable at December 31 (in shares)	340,503
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding - weighted average exercise price per share	$ 11.33
Exercised, weighted average exercise price per share	10.54
Canceled, weighted average exercise price per share	9.81
Vested and Expected to Vest, weighted average exercise price per share	12.11
Exercisable, weighted average exercise price per share	$ 11.94
Outstanding, weighted average remaining contractual term	3 years 6 months	3 years 6 months
Vested and Expected to Vest, weighted average remaining contractual term	3 years 6 months
Exercisable, weighted average remaining contractual term	3 years 3 months 18 days
Options outstanding - aggregate intrinsic value	$ 11,705	$ 15,189
Vested and Expected to Vest, aggregate intrinsic value	11,705
Exercisable, aggregate intrinsic value	11,241
Employee Stock Option [Member]
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Total intrinsic value of options exercised	$ 10,900	$ 3,900	$ 7,600
Incentive Stock Options [Member]
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	4,267
Exercised (in shares)	(4,267)
Canceled (in shares)	0
Outstanding at December 31 (in shares)	0	4,267
Vested and Expected to Vest at December 31(in shares)	0
Exercisable at December 31 (in shares)	0
Non Qualified Stock Options [Member]
Outstanding Stock Options Activity [Roll Forward]
Outstanding at January 1 (in shares)	690,614
Exercised (in shares)	(325,235)
Canceled (in shares)	(8,993)
Outstanding at December 31 (in shares)	356,386	690,614
Vested and Expected to Vest at December 31(in shares)	356,386
Exercisable at December 31 (in shares)	340,503