Schedule IV Reinsurance (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount									$ 1,286,527,000	$ 1,244,870,000	$ 1,074,298,000
Ceded to Other Companies									183,419,000	109,903,000	67,195,000
Assumed from Other Companies									12,213,000	10,382,000	6,904,000
Net Amount	$ 302,140,000	$ 286,471,000	$ 249,295,000	$ 277,415,000	$ 301,486,000	$ 281,185,000	$ 299,166,000	$ 263,512,000	$ 1,115,321,000	$ 1,145,349,000	$ 1,014,007,000
Assumed Premium as a Percentage of Net Premiums									1.10%	0.91%	0.68%
Mortgage Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount									$ 1,263,684,000	$ 1,233,528,000	$ 1,066,860,000
Ceded to Other Companies									183,130,000	109,696,000	67,047,000
Assumed from Other Companies									12,213,000	10,382,000	6,904,000
Net Amount									$ 1,092,767,000	$ 1,134,214,000	$ 1,006,717,000
Assumed Premium as a Percentage of Net Premiums									1.12%	0.92%	0.69%
Title Insurance
SEC Schedule, 12-17, Insurance Companies, Reinsurance [Line Items]
Gross Amount									$ 22,843,000	$ 11,342,000	$ 7,438,000
Ceded to Other Companies									289,000	207,000	148,000
Assumed from Other Companies									0	0	0
Net Amount									$ 22,554,000	$ 11,135,000	$ 7,290,000
Assumed Premium as a Percentage of Net Premiums									0.00%	0.00%	0.00%