STATEMENTS OF CHANGES IN STOCKHOLDER'S EQUITY - USD ($) $ in Millions	Total	Common Stock	Premium on Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2012	$ 2,703.1	$ 100.9	$ 913.1	$ 1,690.4	$ (1.3)
Comprehensive income (loss)
Net income	292.6	0.0	0.0	292.6	0.0
Other comprehensive income, net of tax	1.3	0.0	0.0	0.0	1.3
Dividends declared on common stock	(170.0)	0.0	0.0	(170.0)	0.0
Stock-based compensation	2.3	0.0	2.3	0.0	0.0
Balance at Dec. 31, 2013	2,829.3	100.9	915.4	1,813.0	0.0
Comprehensive income (loss)
Net income	292.0	0.0	0.0	292.0	0.0
Other comprehensive income, net of tax	0.0
Dividends declared on common stock	(120.0)	0.0	0.0	(120.0)	0.0
Stock-based compensation	2.9	0.0	2.9	0.0	0.0
Balance at Dec. 31, 2014	3,004.2	100.9	918.3	1,985.0	0.0
Comprehensive income (loss)
Net income	268.9	0.0	0.0	268.9	0.0
Other comprehensive income, net of tax	0.0
Dividends declared on common stock	(120.0)	0.0	0.0	(120.0)	0.0
Stock-based compensation	2.6	0.0	2.6	0.0	0.0
Balance at Dec. 31, 2015	$ 3,155.7	$ 100.9	$ 920.9	$ 2,133.9	$ 0.0