Employee Benefits and Share-Based Compensation - Stock Purchase Plan (Details) - USD ($) shares in Thousands		12 Months Ended
	May. 19, 2009	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares added to reserved for future issuance	2,600
Shares reserved for future issuance		10,342
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance		3,251
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		$ 25,000
Purchase price of common stock, percent		85.00%
Offering period		24 months
Purchase period		6 months
Shares added to reserved for future issuance	3,000
Shares reserved for future issuance		3,300
Share of common stock purchased		400
Shares issued for the 1997 Employee Stock Purchase Plan		5,100
Unrecognized compensation cost		$ 1,400,000
Weighted average period of compensation cost recognized		6 months 30 days