Pension And Other Postretirement Benefit Plans (Tables)

9 Months Ended

Dec. 31, 2012

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Components of Company's Net Periodic Benefit Cost

	Pension Benefits						Other Postretirement Benefits
	Three Months Ended December 31,						Three Months Ended December 31,
(in thousands of dollars)	2012			2011			2012			2011
Service cost	$	1,229		$	891		$	151		$	188
Interest cost	3,174			3,413			582			578
Expected return on plan assets	(3,544		)	(3,700		)	(31		)	(33		)
Settlement costs	1,975			—			—			—
Net amortization and deferral	2,522			2,384			56			(58		)
Net periodic benefit cost	$	5,356		$	2,988		$	758		$	675

	Pension Benefits						Other Postretirement Benefits
	Nine Months Ended December 31,						Nine Months Ended December 31,
(in thousands of dollars)	2012			2011			2012			2011
Service cost	$	3,499		$	3,455		$	445		$	566
Interest cost	9,493			10,250			1,727			1,734
Expected return on plan assets	(10,238		)	(11,055		)	(93		)	(101		)
Settlement costs	3,304			—			—			—
Net amortization and deferral	7,886			5,061			156			(175		)
Net periodic benefit cost	$	13,944		$	7,711		$	2,235		$	2,024