Compensation Plans: Stock Based (Details) $ / shares in Units, $ in Millions			12 Months Ended
		Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares $ / shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock available for grant		4,400,000	4,400,000
Impact outright issuance of one share has on number of available shares			1
Director [Member]
Director Shares
Shares Issued, Shares, Share-based Payment Arrangement, before Forfeiture			96,719	63,741	71,573
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	0	0	0
Award vesting period		3 years
Multiplier assumed			1
Stock-based compensation expense | $			$ 10.9	$ 10.3	$ 9.7
Unrecognized stock based compensation expense | $		$ 15.9	15.9
Fair value of PSUs/RSUs granted in period | $			$ 10.2	$ 14.0	$ 15.5
Share-based compensation arrangement by share-based payment award, increment vesting period			6 months
Shares Issued in Period			0	0	0
Fair value of PSUs/RSUs Vested in Period | $			$ 9.1	$ 10.3	$ 8.1
Weighted Average Grant Date Fair Value
Non-vested at beginning of year (in shares)	[1]		1,711,259	1,533,491	828,923
Non-vested outstanding at the beginning of the period (in dollars per share) | $ / shares			$ 20.68	$ 22.97	$ 43.25
Granted (in shares)	[1]		793,125	572,924	977,731
Granted (in dollars per share) | $ / shares			$ 12.80	$ 24.45	$ 15.86
Vested (in shares)	[1]		(346,021)	(233,102)	(94,338)
Vested (in dollars per share) | $ / shares			$ 26.32	$ 44.25	$ 85.85
Forfeited (in shares)	[1]		(135,778)	(162,054)	(178,825)
Forfeited (in dollars per share) | $ / shares			$ 16.98	$ 21.79	$ 44.99
Non-vested at end of year (in shares)	[1]	2,022,585	2,022,585	1,711,259	1,533,491
Non-vested outstanding at the end of the period (in dollars per share) | $ / shares		$ 16.87	$ 16.87	$ 20.68	$ 22.97
Performance Shares [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement		0	0
Performance Shares [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Multiplier applied to PSU awards at settlement		2	2
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Stock-based compensation expense | $			$ 11.1	$ 10.8	$ 10.3
Unrecognized stock based compensation expense | $		$ 16.9	16.9
Fair value of PSUs/RSUs granted in period | $			$ 12.1	$ 15.0	$ 17.0
Number of Shares Represented by Each RSU		1	1
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vesting Increment				0.33
Share-based compensation arrangement by share-based payment award, increment vesting period			6 months
Restricted Stock, Shares Settled Gross of Shares for Tax Withholdings	[2]		466,535,000	407,529,000	246,025,000
Shares held for settlement of income and payroll tax obligations (in shares)			(132,136,000)	(115,784,000)	(74,747,000)
Shares Issued in Period			334,399,000	291,745,000	171,278,000
Fair value of PSUs/RSUs Vested in Period | $			$ 10.2	$ 9.9	$ 10.8
Weighted Average Grant Date Fair Value
Non-vested at beginning of year (in shares)			1,243,163	1,244,262	604,116
Non-vested outstanding at the beginning of the period (in dollars per share) | $ / shares			$ 21.50	$ 20.25	$ 37.39
Granted (in shares)			978,932	583,552	1,020,780
Granted (in dollars per share) | $ / shares			$ 12.36	$ 25.77	$ 16.64
Vested (in shares)			(466,535)	(407,529)	(246,025)
Vested (in dollars per share) | $ / shares			$ 21.94	$ 24.30	$ 43.99
Forfeited (in shares)			(223,429)	(177,122)	(134,609)
Forfeited (in dollars per share) | $ / shares			$ 18.16	$ 17.26	$ 26.38
Non-vested at end of year (in shares)		1,532,131	1,532,131	1,243,163	1,244,262
Non-vested outstanding at the end of the period (in dollars per share) | $ / shares		$ 16.01	$ 16.01	$ 21.50	$ 20.25
Restricted Stock Units (RSUs) [Member] | Director [Member]
Weighted Average Grant Date Fair Value
Granted (in shares)					8,794
Shares Issued to the Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $			$ 1.2	$ 1.7	$ 1.6

[1] ⁽¹⁾  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.

[2] ⁽¹⁾  During the years ended December 31, 2019, 2018, and 2017, the Company issued shares of common stock to settle RSUs that related to awards granted in previous years. The Company and a 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.