Parent Company Only Condensed Financial Statements - Consolidated Statements of Cash Flow (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Adjustments to reconcile net income to net cash provided by operating activities
Share-based compensation	$ 3,601	$ 2,950	$ 5,048
Excess tax benefit of share-based compensation	(449)	(205)	(222)
Net cash provided by operating activities	47,187	31,494	29,308
Cash flows from investing activities:
Net cash provided by (used in) investing activities	(337,250)	(212,826)	176,084
Cash flows from financing activities:
Repayments of notes payable	(5,700)	(4,800)	(1,200)
Cash dividends paid	(5,259)	(4,177)	(3,946)
Excess tax benefit of share-based compensation	449	205	222
Issuance of common stock	2	2	1
Common stock repurchased	0	0	(1,006)
Proceeds from the issuance of equity instruments, net	(1,192)	(681)	2,264
Net cash provided (used) by financing activities	283,524	71,459	(111,193)
Net increase (decrease) in cash and cash equivalents	(6,539)	(109,873)	94,199
Cash and cash equivalents, beginning of period	100,696	210,569	116,370
Cash and cash equivalents, end of period	94,157	100,696	210,569
Parent [Member]
Cash flows from operating activities:
Net income available to common shareholders	38,450	27,173	33,104
Adjustments to reconcile net income to net cash provided by operating activities
Share-based compensation	3,601	2,950	5,049
Net income of subsidiaries	(41,298)	(30,560)	(37,876)
Dividends from subsidiaries	10,000	10,000	10,000
Excess tax benefit of share-based compensation	(449)	(205)	(222)
Other, net	848	704	2,004
Net cash provided by operating activities	11,152	10,062	12,059
Cash flows from investing activities:
Purchases of other investments	(2,832)	(2,224)	(761)
Proceeds from distributions on other investments	880	176	243
Net cash provided by (used in) investing activities	(1,952)	(2,048)	(518)
Cash flows from financing activities:
Repayments of notes payable	(5,700)	(4,800)	(1,200)
Cash dividends paid	(5,259)	(4,177)	(3,947)
Excess tax benefit of share-based compensation	449	205	222
Issuance of common stock	2	2	13
Common stock repurchased	0	0	(1,006)
Proceeds from the issuance of equity instruments, net	(1,192)	(681)	2,266
Net cash provided (used) by financing activities	(11,700)	(9,451)	(3,652)
Net increase (decrease) in cash and cash equivalents	(2,500)	(1,437)	7,889
Cash and cash equivalents, beginning of period	14,532	15,969	8,080
Cash and cash equivalents, end of period	$ 12,032	$ 14,532	$ 15,969