Goodwill and Other Intangible Assets - Summary of gross carrying amounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Other intangible assets
Gross carrying amount	$ 119,501	$ 118,415	$ 121,736
Accumulated amortization	(59,882)	(48,039)	(58,836)
Net carrying amount	59,619	70,376	62,900
Amortization expense	3,281	3,413
Estimated amortization expense for other intangibles for each of the next five quarters
June 30, 2019	3,268
September 30, 2019	3,268
December 31, 2019	3,267
March 31, 2020	3,007
June 30, 2020	2,995
Thereafter	43,814
Net carrying amount	$ 59,619	$ 70,376	$ 62,900
Minimum
Other intangible assets
Estimated useful lives	2 years
Maximum
Other intangible assets
Estimated useful lives	15 years