Parent Company only and PSLS - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	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
Operating Activities:
Net income	$ 42,160	$ 11,617	$ 1,454	$ (14,727)	$ 38,658	$ 43,242	$ 10,389	$ 19,422	$ 40,504	$ 111,711	$ 57,036
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Stock-based compensation									121,688	32,003	44,285
Net cash provided by operating activities									779,765	67,798	509,795
Financing Activities:
Repayment of senior notes									0	0	(125,000)
Repurchase of common stock									(21,965)	(50,584)	(70,903)
Payment of cash dividend									(28,172)	(35,594)	(47,157)
Net cash provided by/(used in) financing activities									(87,555)	104,657	(476,769)
Parent Company
Operating Activities:
Net income									40,504	111,711	57,036
Adjustments to reconcile net income/(loss) to net cash provided by operating activities:
Stock-based compensation									525	643	404
Equity in undistributed income of subsidiaries									(16,463)	(99,005)	(5,469)
Net cash provided by operating activities									24,566	13,349	51,971
Financing Activities:
Issuance of senior notes									0	175,000	0
Repayment of senior notes									0	0	(125,000)
Advances from/(to) subsidiaries									25,571	(102,225)	188,995
Repurchase of common stock									(21,965)	(50,584)	(70,903)
Payment of cash dividend									(28,172)	(35,594)	(47,157)
Net cash provided by/(used in) financing activities									(24,566)	(13,403)	(54,065)
Net decrease in cash and cash equivalents									0	(54)	(2,094)
Cash and cash equivalents at beginning of year				$ 200				$ 254	200	254	2,348
Cash and cash equivalents at end of year	$ 200				$ 200				$ 200	$ 200	$ 254