Business Combinations - Estimated Fair Values of Aggregate Assets and Liabilities Acquired (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	$ 8,033
Fixed assets	2,379
Goodwill	277,204
Other assets	3,088
Total assets acquired	392,432
Other current liabilities	(14,089)
Total liabilities assumed	(14,089)
Net assets acquired	378,343
Special Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	1,764
Fixed assets	346
Goodwill	60,049
Total assets acquired	77,778
Other current liabilities	551
Total liabilities assumed	551
Net assets acquired	78,329
Texas Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	446
Fixed assets	27
Goodwill	8,940
Total assets acquired	12,660
Other current liabilities	(1,680)
Total liabilities assumed	(1,680)
Net assets acquired	10,980
Colonial
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	1,344
Fixed assets	59
Goodwill	25,719
Total assets acquired	36,558
Other current liabilities	(1,355)
Total liabilities assumed	(1,355)
Net assets acquired	35,203
RLA
Fair Value Of Assets And Liabilities Statement [Line Items]
Fixed assets	54
Goodwill	51,285
Total assets acquired	64,695
Other current liabilities	(11,443)
Total liabilities assumed	(11,443)
Net assets acquired	53,252
Sterling
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	118
Fixed assets	16
Goodwill	15,163
Total assets acquired	22,514
Other current liabilities	(33)
Total liabilities assumed	(33)
Net assets acquired	22,481
LP
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	3,528
Fixed assets	1,877
Goodwill	115,200
Total assets acquired	169,269
Other current liabilities	(10)
Total liabilities assumed	(10)
Net assets acquired	169,259
Other
Fair Value Of Assets And Liabilities Statement [Line Items]
Other current assets	833
Goodwill	848
Other assets	3,088
Total assets acquired	8,958
Other current liabilities	(119)
Total liabilities assumed	(119)
Net assets acquired	8,839
Purchased Customer Accounts
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	100,960
Purchased Customer Accounts | Special Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	15,483
Purchased Customer Accounts | Texas Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	3,222
Purchased Customer Accounts | Colonial
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	9,393
Purchased Customer Accounts | RLA
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	12,875
Purchased Customer Accounts | Sterling
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	7,196
Purchased Customer Accounts | LP
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	48,633
Purchased Customer Accounts | Other
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	4,158
Non-compete Agreements
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	768
Non-compete Agreements | Special Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	136
Non-compete Agreements | Texas Risk
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	25
Non-compete Agreements | Colonial
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	43
Non-compete Agreements | RLA
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	481
Non-compete Agreements | Sterling
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	21
Non-compete Agreements | LP
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	31
Non-compete Agreements | Other
Fair Value Of Assets And Liabilities Statement [Line Items]
Intangible assets	$ 31