Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount, amortizing intangible assets	$ 111,617	$ 102,187
Accumulated amortization, amortizing intangible assets	75,470	72,654
Net carrying amount, amortizing intangible assets	36,147	29,533
Gross carrying amount, non-amortizing intangible assets	116,717	107,287
Accumulated amortization, non-amortizing intangible assets	41,247	34,633
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount, amortizing intangible assets	98,082	99,080
Accumulated amortization, amortizing intangible assets	73,317	71,036
Net carrying amount, amortizing intangible assets	24,765	28,044
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount, amortizing intangible assets	10,281	0
Accumulated amortization, amortizing intangible assets	253	0
Net carrying amount, amortizing intangible assets	10,028	0
Acquired software
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount, amortizing intangible assets	3,254	3,107
Accumulated amortization, amortizing intangible assets	1,900	1,618
Net carrying amount, amortizing intangible assets	1,354	1,489
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount, non-amortizing intangible assets	$ 5,100	$ 5,100