Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2014

Compensation and Retirement Disclosure [Abstract]

Schedule of Defined Benefit Plans Disclosures

Components of the qualified and nonqualified net periodic pension cost are listed in the table below:

	3 Months Ended						9 Months Ended						12 Months Ended
	September 30,						September 30,						September 30,
	2014			2013			2014			2013			2014			2013
	(in millions)
Service cost	$	2.9		$	3.3		$	8.9		$	10.4		$	12.4		$	13.4
Interest cost	8.3			7.5			25.0			23.0			32.6			31.3
Expected return on plan assets	(11.4		)	(9.5		)	(32.7		)	(28.6		)	(42.2		)	(36.7		)
Prior service and other costs	0.1			0.2			0.4			0.8			0.7			0.8
Recognized net actuarial loss	3.7			8.0			11.6			21.7			18.8			30.4
Net pension cost	$	3.6		$	9.5		$	13.2		$	27.3		$	22.3		$	39.2

Net periodic postretirement benefit cost components are listed in the table below:

	3 Months Ended						9 Months Ended						12 Months Ended
	September 30,						September 30,						September 30,
	2014			2013			2014			2013			2014			2013
	(in millions)
Service cost	$	0.2		$	0.2		$	0.5		$	0.6		$	0.6		$	0.8
Interest cost	0.9			0.9			2.9			2.8			3.8			3.8
Expected return on plan assets	(0.8		)	(0.6		)	(2.3		)	(1.9		)	(3.0		)	(2.5		)
Amortization of transition obligation	—			—			—			—			—			0.4
Recognized net actuarial loss (gain)	(0.1		)	0.8			0.5			2.2			1.3			3.1
Accretion of regulatory liability	0.2			0.2			0.6			0.5			0.6			0.3
Net postretirement benefit cost	$	0.4		$	1.5		$	2.2		$	4.2		$	3.3		$	5.9