Intangible Assets - Balances by Major Asset Class and Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Intangible assets with definite lives
Accumulated Amortization	$ 208,564		$ 193,347
Amortization expense	15,199	$ 15,207
Intangible assets
Gross Carrying Amount	726,695		726,652
Net Carrying Amount	$ 518,131		$ 533,305
Weighted average
Intangible assets with definite lives
Amortization period	12 years 9 months 18 days		12 years 9 months 18 days
Connolly Trademark
Intangible assets with indefinite lives
Gross Carrying Amount	$ 4,200		$ 4,200
Net Carrying Amount	4,200		4,200
Customer relationships
Intangible assets with definite lives
Gross Carrying Amount	640,095		640,052
Accumulated Amortization	156,549		144,768
Net Carrying Amount	$ 483,546		$ 495,284
Customer relationships | Weighted average
Intangible assets with definite lives
Amortization period	13 years 8 months 12 days		13 years 8 months 12 days
Acquired software
Intangible assets with definite lives
Gross Carrying Amount	$ 82,400		$ 82,400
Accumulated Amortization	52,015		48,579
Net Carrying Amount	$ 30,385		$ 33,821
Acquired software | Weighted average
Intangible assets with definite lives
Amortization period	6 years 2 months 12 days		6 years 2 months 12 days