Goodwill and Other Intangible Assets - Summary of gross carrying amounts - (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other intangible assets
Gross carrying amount	$ 82,154	$ 82,154
Accumulated amortization	(42,306)	(34,729)
Net carrying amount	39,848	47,425
Amortization expense	7,577	$ 8,324	$ 8,320
Estimated amortization expense for other intangibles for each of the next five years
2017	7,202
2018	6,729
2019	6,330
2020	5,792
2021	5,188
Thereafter	8,607
Total estimated amortization expense for other intangibles for the next five years	$ 39,848
Minimum
Other intangible assets
Estimated useful lives	2 years
Maximum
Other intangible assets
Estimated useful lives	15 years