Goodwill and Other Intangible Assets - Summary of gross carrying amounts - (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Other intangible assets
Gross carrying amount	$ 100,274	$ 82,154	$ 82,154
Accumulated amortization	(44,813)	(36,633)	(42,306)
Net carrying amount	55,461	45,521	$ 39,848
Amortization expense	2,507	$ 1,904
Estimated amortization expense for other intangibles for each of the next five quarters
December 31, 2016	2,495
March 31, 2017	2,494
June 30, 2017	2,494
September 30, 2017	2,331
December 31, 2017	2,319
Thereafter	$ 43,328
Minimum
Other intangible assets
Estimated useful lives	2 years
Maximum
Other intangible assets
Estimated useful lives	15 years