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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Financial Information (unaudited)
Total Revenues		$ 126,747	$ 114,531	$ 121,581	$ 120,835	$ 119,589	$ 104,185	$ 120,610	$ 124,668	$ 483,694	$ 469,052	$ 634,803
Expenses:
Compensation and employee benefits		45,283	46,755	45,994	46,684	42,980	45,127	48,315	52,464	184,716	188,886	209,323
Transaction processing		26,981	23,428	25,482	24,856	24,540	20,799	22,098	22,834	100,747	90,271	91,492
Occupancy and equipment		23,316	14,945	14,680	15,622	14,296	13,849	14,066	13,978	68,563	56,189	57,495
Telecommunications and data processing services		12,132	12,189	12,129	12,027	13,302	13,720	14,848	14,773	48,477	56,643	51,523
Restructuring charges						5,265		4,355			9,620
Other general and administrative		18,957	18,670	17,699	17,315	20,803	37,927	26,014	23,722	72,641	108,466	101,915
Interest expense		496	499	510	520	549	561	572	535	2,025	2,217	1,829
Total expenses		127,165	116,486	116,494	117,024	121,735	131,983	130,268	128,306
Income (loss) before income tax expense (benefit)		(418)	(1,955)	5,087	3,811	(2,146)	(27,798)	(9,658)	(3,638)	6,525	(43,240)	121,226
Income tax expense (benefit)	$ 6,500	2,000	45,012	444	(1,491)	(7,862)	(3,887)	(4,441)	(1,132)	45,965	(17,322)	29,656
Net (loss) income		$ (2,418)	$ (46,967)	$ 4,643	$ 5,302	$ 5,716	$ (23,911)	$ (5,217)	$ (2,506)	$ (39,440)	$ (25,918)	$ 91,570
Basic (loss) income per share (in dollars per share)		$ (0.07)	$ (1.42)	$ 0.14	$ 0.16	$ 0.18	$ (0.73)	$ (0.16)	$ (0.08)	$ (1.19)	$ (0.79)	$ 2.70
Diluted (loss) income per share (in dollars per share)		$ (0.07)	$ (1.42)	$ 0.14	$ 0.16	$ 0.17	$ (0.73)	$ (0.16)	$ (0.08)	$ (1.19)	$ (0.79)	$ 2.63
Basic weighted average number of common shares outstanding (in shares)		32,855	33,105	33,125	32,949	32,607	32,725	33,189	33,106	33,009	32,906	33,907
Diluted weighted average number of common shares outstanding (in shares)		32,855	33,105	34,222	34,130	33,988	32,725	33,189	33,106	33,009	32,906	34,815