Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan Stock-based Compensation: Incentive Award Plan and Employee Stock Purchase Plan (RSU and RSAs) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)	$ 36.31
Award with service conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	705,373
Granted (in shares)	213,649
Market value share count adjustment for liability awards (in shares)	0
Vested (in shares)	(423,280)
Forfeited (in shares)	(30,373)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	465,369	705,373
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	437,699
Awards with performance and service conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	381,188
Granted (in shares)	712,108
Market value share count adjustment for liability awards (in shares)	(18,619)
Vested (in shares)	(204,936)
Forfeited (in shares)	(25,728)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	881,251	381,188
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	826,620
Restricted Stock Units and Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1 (in shares)	1,086,561
Granted (in shares)	925,757
Market value share count adjustment for liability awards (in shares)	(18,619)
ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentOtherThanOptionsMarketValueShareCountAdjustmentWeightedAverageGrantDateFairValue	$ 35.09
Vested (in shares)	(628,216)
Forfeited (in shares)	(56,101)
Unvested RSUs and RSAs outstanding at December 31 (in shares)	1,346,620	1,086,561
Unvested and expected to vest RSUs and RSAs outstanding at December 31 (in shares)	1,264,319
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Unvested RSUs and RSAs outstanding at January 1, weighted average grant date fair value (in dollars per share)	$ 24.88
Granted, weighted average grant date fair value (in dollars per share)	40.49	$ 33.66	$ 26.17
Vested, weighted average grant date fair value (in dollars per share)	24.76
Unvested RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)		$ 24.88
Unvested and expected to vest RSUs and RSAs outstanding at December 31, weighted average grant date fair value (in dollars per share)	$ 36.05
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures	31.38