Compensation Plans: Stock Based (Details) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2016 USD ($) shares $ / shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant		5,500,000
Impact outright issuance of one share has on number of available shares		1
Stock-based compensation expense | $		$ 26,897	$ 27,467	$ 32,694
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum Impact of issuance of one performance share award on available shares under the equity incentive plan		2
Multiplier Applied to PSU Awards at Settlement		0.2	1.0	0.55
Award Vesting Period		3 years
Stock-based compensation expense | $		$ 11,000	$ 10,600	$ 16,000
Unrecognized stock based compensation expense | $		$ 15,900
Multiplier assumed		1
Fair value of PSUs/RSUs Granted in Period | $		$ 11,900	$ 14,500	$ 19,200
Performance Share Units Shares Settled Gross of Shares for Tax Withholdings	[1]	44,870	288,962	130,163
Shares held for settlement of income and payroll tax obligations (in shares)		(14,809)	(100,683)	(45,042)
Shares Issued in Period		30,061	188,279	85,121
Fair value of PSUs/RSUs Vested in Period | $		$ 8,400	$ 4,000	$ 13,400
Weighted Average Grant Date Fair Value
Non-vested at beginning of year (in shares)	[2]	626,328	433,660	572,469
Granted (in shares)	[2]	447,971	320,753	202,404
Vested (in shares)	[2]	(130,353)	(76,438)	(206,830)
Forfeited (in shares)	[2]	(115,023)	(51,647)	(134,383)
Non-vested at end of year (in shares)	[2]	828,923	626,328	433,660
Non-vested outstanding at the beginning of the period (in dollars per share) | $ / shares	[2]	$ 61.81	$ 73.63	$ 66.07
Granted (in dollars per share) | $ / shares	[2]	26.56	45.34	94.66
Vested (in dollars per share) | $ / shares	[2]	64.17	51.76	64.79
Forfeited (in dollars per share) | $ / shares	[2]	55.59	73.62	86.72
Non-vested outstanding at the end of the period (in dollars per share) | $ / shares	[2]	$ 43.25	$ 61.81	$ 73.63
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $		$ 11,900	$ 13,400	$ 13,900
Unrecognized stock based compensation expense | $		14,400
Fair value of PSUs/RSUs Granted in Period | $		$ 11,700	$ 15,600	$ 19,700
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Increment		0.33	0.33	0.33
Shares held for settlement of income and payroll tax obligations (in shares)		(72,181)	(91,045)	(81,434)
Shares Issued in Period		169,182	187,244	171,597
Fair value of PSUs/RSUs Vested in Period | $		$ 14,000	$ 17,600	$ 14,700
Number of Shares Represented by Each RSU		1
Restricted Stock, Shares Settled Gross of Shares for Tax Withholdings	[3]	241,363	278,289	253,031
Weighted Average Grant Date Fair Value
Non-vested at beginning of year (in shares)		543,737	515,724	580,431
Granted (in shares)		417,065	356,246	234,560
Vested (in shares)		(241,363)	(278,289)	(253,031)
Forfeited (in shares)		(115,323)	(49,944)	(46,236)
Non-vested at end of year (in shares)		604,116	543,737	515,724
Non-vested outstanding at the beginning of the period (in dollars per share) | $ / shares		$ 55.01	$ 68.29	$ 57.05
Granted (in dollars per share) | $ / shares		28.08	43.72	83.98
Vested (in dollars per share) | $ / shares		58.06	63.12	58.19
Forfeited (in dollars per share) | $ / shares		43.52	66.53	62.06
Non-vested outstanding at the end of the period (in dollars per share) | $ / shares		$ 37.39	$ 55.01	$ 68.29
Shares Issued to the Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award Vesting Period		1 year
Stock-based compensation expense | $		$ 2,000	$ 1,600	$ 1,600
Director Shares
Stock Issued During Period, Shares, Share-based Compensation, Gross		53,473	39,903	27,677
Minimum Service Requirement for Immediate Vesting of Granted Shares		5 years
Minimum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier Applied to PSU Awards at Settlement		0
Maximum [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier Applied to PSU Awards at Settlement		2

[1] During the years ended December 31, 2016, 2015, and 2014, the Company issued shares of common stock for PSUs granted in 2013, 2012, and 2011. The Company and the majority of grant recipients mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings in accordance with the Company’s Equity Plan and individual award agreements.

[2] The number of awards assumes a multiplier of one. The final number of shares of common stock issued may vary depending on the three-year performance multiplier, which ranges from zero to two.

[3] During the years ended December 31, 2016, 2015, and 2014, the Company issued shares of common stock for RSUs granted in previous years. The Company and the majority of grant recipients mutually agreed to net share settle a portion of the awards to cover income and payroll tax withholdings in accordance with the Company’s Equity Plan and individual award agreements.