SCHEDULE II - Condensed Financial Information of Registrant (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 20,471	$ (25,167)	$ 20,307	$ 22,728	$ 11,632	$ 19,581	$ 16,984	$ 15,633	$ 38,339	$ 63,830	$ 43,566
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for depreciation and amortization									4,063	4,215	2,123
Share based compensation expense									7,178	6,228	7,688
Net cash provided by operating activities									1,489,022	290,028	207,816
Investing activities
Net cash used in investing activities									(263,359)	(266,772)	(104,741)
Financing activities
Dividends paid									(36,720)	(36,123)	(50,832)
Senior debt issuance									60,000	20,000	10,000
Senior debt repayments									(20,000)	0	0
Issuances of common shares under equity incentive plans									8,286	5,172	1,708
Common share repurchases									(2,899)	(2,239)	(9,448)
Net cash provided by (used in) financing activities									7,956	(14,294)	(49,364)
Cash and cash equivalents at beginning of year				172,457					172,457
Cash and cash equivalents at end of year	206,912				172,457				206,912	172,457
Supplemental information
Interest paid									12,354	11,269	8,909
Parent Company
Operating activities
Net income									38,339	63,830	43,566
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provision for depreciation and amortization									182	176	176
Share based compensation expense									7,178	6,228	7,688
Equity in undistributed earnings of subsidiaries									(49,592)	6,000	(23,662)
Changes in operating assets and liabilities:									(2,782)	(5,653)	684
Net cash provided by operating activities									(6,675)	70,581	28,452
Investing activities
Dividends from subsidiaries									0	0	20,000
Net cash used in investing activities									0	0	20,000
Financing activities
Dividends paid									(36,720)	(36,123)	(50,832)
Senior debt issuance									60,000	20,000	10,000
Senior debt repayments									(20,000)	0	0
Subsidiary note repayments									0	(60,000)	0
Debt issue costs paid									(711)	0	0
Issuances of common shares under equity incentive plans									8,286	5,172	1,708
Common share repurchases									(2,899)	(2,239)	(9,448)
Net cash provided by (used in) financing activities									7,956	(73,190)	(48,572)
Increase in cash and cash equivalents									1,281	(2,609)	(120)
Cash and cash equivalents at beginning of year				$ 240				$ 2,849	240	2,849	2,969
Cash and cash equivalents at end of year	$ 1,521				$ 240				1,521	240	2,849
Supplemental information
Interest paid									$ 5,710	$ 5,052	$ 4,612