Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities - Significant Non-Cash Investing and Financing Activities (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Restricted Cash and Cash Equivalents Items [Line Items]
Document Period End Date	Jun. 30, 2017
Cash and cash equivalents	$ 600,296,000	$ 453,939,000	$ 515,646,000	$ 443,420,000
Restricted Cash and Cash Equivalents	276,634,000	277,646,000	265,637,000	229,753,000
Cash paid during the period for:
Interest	18,556,000	18,770,000
Income taxes	77,343,000	71,466,000
Significant non-cash investing and financing activities
Other payable issued for purchased customer accounts	11,069,000	10,500,000
Estimated acquisition earn-out payables and related charges	282,000	2,393,000
Business Acquisition Cost of Entity Note Payable	0	492,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 876,930,000	$ 731,585,000	$ 781,283,000	$ 673,173,000