Supplementary Financial Information - Expenses and Revenue (unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplementary Financial Information (unaudited)
Total Revenues		$ 119,589	$ 104,185	$ 120,610	$ 124,668	$ 224,173	$ 120,409	$ 140,494	$ 149,727	$ 469,052	$ 634,803	$ 559,814
Expenses:
Compensation and employee benefits		42,980	45,127	48,315	52,464	51,711	46,305	53,899	57,408	188,886	209,323	215,758
Transaction processing		24,540	20,799	22,098	22,834	20,111	21,621	25,187	24,573	90,271	91,492	86,400
Occupancy and equipment		14,296	13,849	14,066	13,978	14,424	14,229	14,470	14,372	56,189	57,495	59,811
Telecommunications and data processing services		13,302	13,720	14,848	14,773	12,961	12,779	13,011	12,772	56,643	51,523	51,187
Restructuring charge		5,265		4,355						9,620
Other general and administrative		20,803	37,927	26,014	23,722	19,894	21,856	42,408	17,757	108,466	101,915	79,349
Interest expense		549	561	572	535	427	429	468	505	2,217	1,829	2,322
Total expenses		121,735	131,983	130,268	128,306	119,528	117,219	149,443	127,387
(Loss) income before income tax (benefit) expense		(2,146)	(27,798)	(9,658)	(3,638)	104,645	3,190	(8,949)	22,340	(43,240)	121,226	64,987
Income tax (benefit) expense	$ 6,500	(7,862)	(3,887)	(4,441)	(1,132)	22,308	480	1,261	5,607	(17,322)	29,656	14,095
Net (loss) income		$ 5,716	$ (23,911)	$ (5,217)	$ (2,506)	$ 82,337	$ 2,710	$ (10,210)	$ 16,733	$ (25,918)	$ 91,570	$ 50,892
Basic earnings (loss) per share (in dollars per share)		$ 0.18	$ (0.73)	$ (0.16)	$ (0.08)	$ 2.46	$ 0.08	$ (0.30)	$ 0.49	$ (0.79)	$ 2.70	$ 1.44
Diluted earnings (loss) per share (in dollars per share)		$ 0.17	$ (0.73)	$ (0.16)	$ (0.08)	$ 2.40	$ 0.08	$ (0.30)	$ 0.47	$ (0.79)	$ 2.63	$ 1.40
Basic weighted average number of common shares outstanding (in shares)		32,607	32,725	33,189	33,106	33,433	33,859	34,076	34,268	32,906	33,907	35,349
Diluted weighted average number of common shares outstanding (in shares)		33,988	32,725	33,189	33,106	34,359	34,547	34,076	34,451	32,906	34,815	36,365