Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities [Abstract]
Net income	$ 99,897	$ 118,703	$ 85,887
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of property, equipment and internal-use software	49,489	38,581	33,470
Amortization of intangible assets	32,616	32,761	31,110
Provision for uncollectible overdrawn accounts	86,451	79,790	77,145
Employee stock-based compensation	29,583	50,093	40,734
Amortization of (discount) premium on available-for-sale investment securities	(117)	1,042	1,510
Change in fair value of contingent consideration	(1,866)	3,298	(9,672)
Amortization of deferred financing costs	1,334	1,594	1,589
Impairment of capitalized software	578	922	1,326
Deferred income tax expense (benefit)	6,876	(234)	2,780
Changes in operating assets and liabilities:
Accounts receivable, net	(105,052)	(85,455)	(68,368)
Prepaid expenses and other assets	(12,032)	(9,930)	(16,841)
Deferred expenses	4,310	590	(2,098)
Accounts payable and other accrued liabilities	(8,145)	12,471	27,982
Deferred revenue	(6,711)	4,675	4,689
Income tax receivable/payable	11,682	(1,253)	5,067
Other, net	1,021	3,403	2,000
Net cash provided by operating activities	189,914	251,051	218,310
Investing activities [Abstract]
Purchases of available-for-sale investment securities	(189,066)	(186,884)	(58,665)
Proceeds from maturities of available-for-sale securities	110,971	60,449	71,338
Proceeds from sales of available-for-sale securities	4,915	78,385	40,310
Payments for acquisition of property and equipment	(78,214)	(61,030)	(44,142)
Net increase in loans	(2,459)	(5,887)	(12,511)
Business acquisition, net of cash acquired	0	0	(141,493)
Net cash used in investing activities	(153,853)	(114,967)	(145,163)
Financing activities [Abstract]
Borrowings from notes payable	0	0	20,000
Repayments of borrowings from notes payable	(60,000)	(22,500)	(42,500)
Borrowings on revolving line of credit	35,000	0	335,000
Repayments on revolving line of credit	0	0	(335,000)
Proceeds from exercise of options	7,226	21,880	24,161
Taxes paid related to net share settlement of equity awards	(21,338)	(46,007)	(18,077)
Net increase (decrease) in deposits	146,100	(16,733)	284,766
Net (decrease) increase in obligations to customers	(66,760)	17,255	(20,926)
Contingent consideration payments	(4,634)	(4,856)	(3,104)
Repurchase of Class A common stock	(100,000)	0	(51,969)
Deferred financing costs	(719)	0	(164)
Net cash used in financing activities	(65,125)	(50,961)	192,187
Net (decrease) increase in unrestricted cash, cash equivalents and restricted cash	(29,064)	85,123	265,334
Unrestricted cash, cash equivalents and restricted cash, beginning of period	1,095,218	1,010,095	744,761
Unrestricted cash, cash equivalents and restricted cash, end of period	1,066,154	1,095,218	1,010,095
Supplemental Cash Flow Information [Abstract]
Cash paid for interest	2,452	4,888	4,520
Cash paid for income taxes	1,921	6,233	9,603
Total unrestricted cash, cash equivalents and restricted cash, end of period	$ 1,066,154	$ 1,010,095	$ 1,010,095