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, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Increase (Decrease) in Notes Receivables	$ 2,045,000	$ 0
Document Period End Date	Jun. 30, 2019
Cash and cash equivalents	$ 432,548,000	477,928,000	$ 438,961,000	$ 573,383,000
Restricted Cash and Cash Equivalents	382,233,000	309,231,000	338,635,000	250,705,000
Cash paid during the period for:
Interest	26,652,000	19,112,000
Income taxes	61,145,000	65,521,000
Significant non-cash investing and financing activities
Other payable issued for purchased customer accounts	2,159,000	2,386,000
Estimated acquisition earn-out payables and related charges	23,966,000	22,071,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and Cash Equivalents, Period Increase (Decrease)	37,185,000	(36,929,000)
Cash and cash equivalents	$ 814,781,000	$ 787,159,000	$ 777,596,000	$ 824,088,000