CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Millions	Total	Common Stock	Premium on Common Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2014	$ 3,244.4	$ 2.0	$ 1,085.6	$ 2,198.2	$ (41.4)
Comprehensive income (loss)
Net income	43.2	0.0	0.0	43.2	0.0
Other comprehensive income, net of tax	0.2	0.0	0.0	0.0	0.2
Dividends declared on common stock	(49.9)	0.0	0.0	(49.9)	0.0
Issuance of common stock	3.2	0.0	3.2	0.0	0.0
Stock-based compensation	0.7	0.0	0.7	0.0	0.0
Balance at Mar. 31, 2015	3,241.8	2.0	1,089.5	2,191.5	(41.2)
Balance at Dec. 31, 2015	3,326.0	2.0	1,099.3	2,259.8	(35.1)
Comprehensive income (loss)
Net income	25.2	0.0	0.0	25.2	0.0
Other comprehensive income, net of tax	0.4	0.0	0.0	0.0	0.4
Dividends declared on common stock	(54.9)	0.0	0.0	(54.9)	0.0
Stock-based compensation	1.6	0.0	1.6	0.0	0.0
Balance at Mar. 31, 2016	$ 3,298.3	$ 2.0	$ 1,100.9	$ 2,230.1	$ (34.7)