Employee Benefit Plans (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2012 plan subsidiary	Dec. 31, 2011	Dec. 31, 2010
Defined benefit plans disclosure
Number of defined benefit pension plans		3
United Kingdom Defined Benefit Pension Plans
Defined benefit plans disclosure
Number of defined benefit pension plans		2
Sponsored defined benefit pension plans, number of subsidiaries		2
Components of Net Periodic Benefit Cost:
Service cost		$ 4,172,000	$ 4,296,000	$ 3,682,000
Interest cost		7,734,000	8,388,000	7,718,000
Expected return on plan assets		(10,319,000)	(10,569,000)	(8,996,000)
Amortization of net actuarial loss		1,172,000	1,344,000	1,249,000
Expected participant contributions		(1,838,000)	(1,871,000)	(2,074,000)
Net periodic benefit cost		921,000	1,588,000	1,579,000
Assumptions Used to Determine Net Periodic Benefit Cost:
Discount rate (as a percent)		4.60%	5.20%	5.75%
Expected rate of return on assets (as a percent)		5.90%	6.50%	6.75%
Salary increases (as a percent)		4.00%	4.50%	4.50%
Change in Projected Benefit Obligation:
Benefit obligation, beginning of year		167,711,000	156,604,000
Service cost		4,172,000	4,296,000	3,682,000
Interest cost		7,734,000	8,388,000	7,718,000
Participant contributions		1,838,000	1,871,000
Actuarial (gain) loss		(2,389,000)	(1,138,000)
Benefits paid		(2,525,000)	(2,348,000)
Foreign currency exchange rate changes		6,291,000	1,909,000
Benefit obligation, end of year		180,994,000	167,711,000	156,604,000
Change in Fair Value of Assets:
Fair value of plan assets, beginning of the year		170,413,000	153,684,000
Employer contributions		6,369,000	6,556,000
Participant contributions		1,838,000	1,871,000
Actual return on plan assets		13,125,000	8,911,000
Benefits paid		(2,525,000)	(2,348,000)
Foreign currency exchange rate changes		6,697,000	1,739,000
Fair value of plan assets, end of the year		195,917,000	170,413,000	153,684,000
Funded status at end of year-over (under) funded		14,923,000	2,702,000
Amount recognized in the consolidated balance sheets:
Non-current assets		14,923,000	2,702,000
Total		14,923,000	2,702,000
Expected employer contributions in next fiscal year		6,400,000
Accumulated benefit obligation		156,400,000	138,500,000
Amounts recognized in accumulated other comprehensive income
Net actuarial loss		33,039,000	40,054,000
Less: Tax benefit (deferred tax asset)		(8,780,000)	(10,722,000)
Accumulated other comprehensive income impact		24,259,000	29,332,000
Net actuarial loss estimated to be amortized from accumulated other comprehensive income into net periodic pension cost in 2013		600,000
Assumptions Used to Determine Benefit Obligations:
Discount rate (as a percent)		4.60%	4.60%
Salary increases (as a percent)		3.60%	4.00%
German Defined Benefit Pension Plan
Defined benefit plans disclosure
Number of defined benefit pension plans		1
Sponsored defined benefit pension plans, number of subsidiaries		1
Components of Net Periodic Benefit Cost:
Service cost		670,000	869,000	754,000
Interest cost		642,000	610,000	584,000
Amortization of net actuarial loss			116,000	74,000
Net periodic benefit cost		1,312,000	1,595,000	1,412,000
Assumptions Used to Determine Net Periodic Benefit Cost:
Discount rate (as a percent)		5.40%	4.60%	5.50%
Salary increases (as a percent)		2.50%	2.50%	3.00%
Change in Projected Benefit Obligation:
Benefit obligation, beginning of year		12,810,000	12,562,000
Service cost		670,000	869,000	754,000
Interest cost		642,000	610,000	584,000
Actuarial (gain) loss	6,100,000	3,991,000	(1,025,000)
Curtailment gain	(700,000)	(657,000)
Benefits paid		(132,000)	(141,000)
Foreign currency exchange rate changes		304,000	(65,000)
Benefit obligation, end of year		17,628,000	12,810,000	12,562,000
Change in Fair Value of Assets:
Benefits paid		(132,000)	(141,000)
Funded status at end of year-over (under) funded		(17,628,000)	(12,810,000)
Amount recognized in the consolidated balance sheets:
Current liabilities		(204,000)	(184,000)
Non-current liabilities		(17,424,000)	(12,626,000)
Total		(17,628,000)	(12,810,000)
Accumulated benefit obligation		15,200,000	10,400,000
Amounts recognized in accumulated other comprehensive income
Net actuarial loss		5,146,000	1,839,000
Less: Tax benefit (deferred tax asset)	(1,900,000)	(1,583,000)	(558,000)
Accumulated other comprehensive income impact		3,563,000	1,281,000
Net actuarial loss estimated to be amortized from accumulated other comprehensive income into net periodic pension cost in 2013		200,000
Assumptions Used to Determine Benefit Obligations:
Discount rate (as a percent)		3.50%	5.40%
Salary increases (as a percent)		2.00%	2.50%
Supplemental Executive Retirement Plan
Defined benefit plans disclosure
Number of defined benefit pension plans		1
Components of Net Periodic Benefit Cost:
Service cost		1,478,000	1,282,000	1,391,000
Interest cost		776,000	695,000	693,000
Amortization of prior service credit		(119,000)	(119,000)	(119,000)
Amortization of net actuarial loss		270,000	296,000	226,000
Net periodic benefit cost		2,405,000	2,154,000	2,191,000
Assumptions Used to Determine Net Periodic Benefit Cost:
Discount rate (as a percent)		4.30%	4.40%	5.25%
Salary increases (as a percent)		3.75%	4.00%	4.00%
Change in Projected Benefit Obligation:
Benefit obligation, beginning of year		16,572,000	14,525,000
Service cost		1,478,000	1,282,000	1,391,000
Interest cost		776,000	695,000	693,000
Actuarial (gain) loss		2,289,000	70,000
Benefit obligation, end of year		21,115,000	16,572,000	14,525,000
Change in Fair Value of Assets:
Funded status at end of year-over (under) funded		(21,115,000)	(16,572,000)
Amount recognized in the consolidated balance sheets:
Current liabilities		(2,486,000)
Non-current liabilities		(18,629,000)	(16,572,000)
Total		(21,115,000)	(16,572,000)
Accumulated benefit obligation		18,800,000	14,100,000
Amounts recognized in accumulated other comprehensive income
Net actuarial loss		6,011,000	3,992,000
Prior service credit		(689,000)	(808,000)
Less: Tax benefit (deferred tax asset)		(1,879,000)	(1,124,000)
Accumulated other comprehensive income impact		3,443,000	2,060,000
Net actuarial loss estimated to be amortized from accumulated other comprehensive income into net periodic pension cost in 2013		600,000
Prior service credit estimated to be amortized from accumulated other comprehensive income into net periodic pension cost in 2013		(100,000)
Assumptions Used to Determine Benefit Obligations:
Discount rate (as a percent)		3.20%	4.30%
Salary increases (as a percent)		3.25%	3.75%
Post-Employment Retiree Health and Welfare Plan
Defined benefit plans disclosure
Number of post-employment retiree health and welfare plan		1
Components of Net Periodic Benefit Cost:
Service cost		69,000	96,000	108,000
Interest cost		290,000	306,000	314,000
Amortization of net actuarial loss		40,000	133,000	33,000
Net periodic benefit cost		399,000	535,000	455,000
Assumptions Used to Determine Net Periodic Benefit Cost:
Discount rate (as a percent)		4.60%	4.70%	5.25%
Health care cost trend rate (as a percent)		8.00%	8.50%	7.50%
Health care cost ultimate trend rate (as a percent)		5.00%
Change in Projected Benefit Obligation:
Benefit obligation, beginning of year		6,540,000	6,224,000
Service cost		69,000	96,000	108,000
Interest cost		290,000	306,000	314,000
Participant contributions		774,000	667,000
Actuarial (gain) loss		(114,000)	179,000
Benefits paid		(912,000)	(1,004,000)
Federal subsidy on benefits paid		170,000	72,000
Benefit obligation, end of year		6,817,000	6,540,000	6,224,000
Change in Fair Value of Assets:
Participant contributions		774,000	667,000
Benefits paid		(912,000)	(1,004,000)
Funded status at end of year-over (under) funded		(6,817,000)	(6,540,000)
Amount recognized in the consolidated balance sheets:
Current liabilities		(607,000)	(614,000)
Non-current liabilities		(6,210,000)	(5,926,000)
Total		(6,817,000)	(6,540,000)
Expected employer contributions in next fiscal year		600,000
Amounts recognized in accumulated other comprehensive income
Net actuarial loss		678,000	832,000
Less: Tax benefit (deferred tax asset)		(239,000)	(294,000)
Accumulated other comprehensive income impact		$ 439,000	$ 538,000
Assumptions Used to Determine Benefit Obligations:
Discount rate (as a percent)		3.60%	4.60%
Health care cost trend rate (as a percent)		7.50%	8.00%