Retirement Benefits - Additional Information (Detail)	12 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended			6 Months Ended			12 Months Ended
	Dec. 31, 2013 USD ($)	Jun. 30, 2013 Pension Benefits, U.S. Plans USD ($)	Jun. 30, 2013 Pension Benefits, U.S. Plans	Dec. 31, 2012 Pension Benefits, U.S. Plans	Sep. 30, 2013 Foreign Pension Plans, Defined Benefit [Member]	Jun. 30, 2013 Foreign Pension Plans, Defined Benefit [Member] USD ($)	Jun. 30, 2013 Foreign Pension Plans, Defined Benefit [Member] GBP (£)	Jun. 30, 2013 Foreign Pension Plans, Defined Benefit [Member] USD ($)	Jun. 30, 2013 Foreign Pension Plans, Defined Benefit [Member] GBP (£)	Jun. 30, 2013 Defined Contribution Pension [Member] USD ($)	Dec. 31, 2014 Defined Contribution Pension [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Before-tax Change in Pension Liability Due to US Pension Plan Amendment		$ (327,400,000)
Defined Benefit Plan, Income Tax on Change in AOCI due to US Pension Plan Amendment		(114,600,000)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate		5.00%	5.00%	4.50%
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Return on Assets			7.50%	7.50%
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments		(700,000)
Average Remaining Life Expectancy of Plan Participants		30 years		11 years
Consultation Period for U.K. Pension Plan					60
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year	33,300,000
Pension, Amount that will be recognized from AOCI to Income, after tax	21,900,000
Defined Contribution Plan, Employer Matching Contribution, Percent										3.00%	5.00%
Defined Contribution Plan, Employer Matching Contribution on amts over 3%										0.50
Defined Contribution Plan, Employer Matching Contribution % for $0.50										2.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount											4.50%
Description of Defined Contribution Pension and Other Postretirement Plans			We have no regulatory contribution requirements for our U.S. qualified defined benefit plan in 2013
Pension Contributions		$ 50,000,000				$ 900,000	£ 600,000	$ 1,900,000	£ 1,200,000