Employee Benefits and Share-Based Compensation - Stock Purchase Plan (Details) - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
	May 19, 2009	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares added to reserved for future issuance (in shares)	2,600
Shares reserved for future issuance (in shares)		9,907
1997 Employee Stock Purchase Plan | Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of earnings allowed for purchase of shares		15.00%
Maximum fair market value of shares		$ 25
Purchase price of common stock, percent		85.00%
Shares added to reserved for future issuance (in shares)	3,000
Shares reserved for future issuance (in shares)		2,831
Share of common stock purchased		400
Shares issued for the 1997 Employee Stock Purchase Plan		5,500
Unrecognized compensation cost		$ 3,500
Weighted average period of compensation cost recognized		14 months 30 days