Acquisitions and Dispositions Martin Currie (Pension Details) (Details) £ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2018 GBP (£)	Mar. 31, 2018 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation, Foreign Currency Translation Gain (Loss)			$ 11,265,000	$ (12,139,000)
Defined Benefit Plan, Benefit Obligation, Business Combination			97,137,000	90,010,000
Defined Benefit Plan, Benefit Obligation, Benefits Paid			(2,451,000)	(1,946,000)
Defined Benefit Plan, Interest Cost			2,763,000	2,904,000	$ 3,268,000
Defined Benefit Plan, Plan Assets, Benefits Paid			(2,451,000)	(1,946,000)
Defined Benefit Plan, Plan Assets, Foreign Currency Translation Gain (Loss)			(7,224,000)	(7,648,000)
Defined Benefit Plan, Plan Assets, Contributions by Employer			1,934,000	1,945,000
Defined Benefit Plan, Expected Return (Loss) on Plan Assets			(3,152,000)	(2,811,000)	(3,176,000)
Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss)			(6,245,000)	18,308,000
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			(389,000)	93,000	92,000
Defined Benefit Plan, Fair Value of Plan Assets				59,623,000	57,253,000		$ 67,529,000
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax			492,000
Defined Benefit Plan, Benefit Obligation				97,137,000			102,469,000
Defined Benefit Plan, Plan Assets, Increase (Decrease) for Actual Return (Loss)			1,199,000	10,019,000
Martin Currie [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Expected Long-term Rate of Return on Plan Assets	5.40%	5.40%
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			$ (389,000)	93,000	$ 92,000
Defined Benefit Plan, Fair Value of Plan Assets				59,623,000			67,529,000
Defined Benefit Plan, Benefit Obligation				97,137,000			102,469,000
Defined Benefit Plan, Funded (Unfunded) Status of Plan				(37,514,000)			(34,940,000)
Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax				$ (16,681,000)			(13,635,000)
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months							1,599,000.000
Defined Benefit Plan, Expected Future Benefit Payment, Year Two							1,673.000
Defined Benefit Plan, Expected Future Benefit Payment, Year Three							2,426.000
Defined Benefit Plan, Expected Future Benefit Payment, Year Four							2,831.000
Defined Benefit Plan, Expected Future Benefit Payment, Year Five							2,701.000
Defined Benefit Plan, Assumptions Used Calculating Net Periodic Benefit Cost, Discount Rate	2.70%	2.70%
Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year							0
Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year						£ 2,320	3,256,000
Defined Benefit Plan, Expected Future Employer Contributions, Current Fiscal Year, Description							16,940.000
DefinedBenefitPlanExpectedFutureEmployerContributionFinal						£ 1	$ 2,050,000
Fair Value, Inputs, Level 2 [Member] | Bonds [Member] | Martin Currie [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations				35.00%		35.00%	35.00%
Defined Benefit Plan, Target Allocation Percentage	0.4
Fair Value, Inputs, Level 1 [Member] | Cash [Member] | Martin Currie [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations						1.00%	1.00%
Fair Value, Inputs, Level 1 [Member] | Equity [Member] | Martin Currie [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Actual Plan Asset Allocations				65.00%		64.00%	64.00%
Defined Benefit Plan, Target Allocation Percentage	0.6