Goodwill and Other Intangible Assets - Summary of gross carrying amounts - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Other intangible assets
Gross carrying amount	$ 100,274	$ 82,154	$ 100,274	$ 82,154	$ 82,154
Accumulated amortization	(47,308)	(38,525)	(47,308)	(38,525)	(42,306)
Net carrying amount	52,966	43,629	52,966	43,629	$ 39,848
Amortization expense	2,495	1,892	5,002	3,795
Amortization of Intangible Assets	2,495	$ 1,892	5,002	$ 3,795
Estimated amortization expense for other intangibles for each of the next five quarters
September 30, 2017	2,494		2,494
December 31, 2017	2,494		2,494
March 31, 2018	2,331		2,331
June 30, 2018	2,319		2,319
September 30, 2018	2,318		2,318
Thereafter	$ 41,010		$ 41,010
Minimum
Other intangible assets
Estimated useful lives			2 years
Maximum
Other intangible assets
Estimated useful lives			15 years