New Accounting Standards	9 Months Ended
Sep. 30, 2017
Accounting Policies [Abstract]
New Accounting Standards	New Accounting Standards Issued In March 2017, the Financial Accounting Standards Boards (FASB) issued an accounting standards update (ASU) related to premium amortization on purchased callable debt securities. The intent of the standard is to shorten the amortization period for certain purchased callable debt securities held at a premium. Under the ASU, the premium is required to be amortized to the earliest call date. The ASU more closely aligns interest income recorded on bonds held at a premium with the economics of the underlying instrument. The ASU, which is required to be applied on a modified retrospective basis, is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Since we have historically used a yield-to-worst scenario for our securities that were purchased at a premium, and the first call on a premium security most often produces the lowest and most conservative yield, we do not expect this standard to have a significant impact on our financial condition, cash flows, or results of operations. Adopted On January 1, 2017, we adopted the ASU to simplify the accounting for employee share-based payment transactions. There were several provisions that could be adopted under this ASU. We did not elect to make any changes to our method of recording forfeitures and are continuing to withhold taxes at the minimum statutory tax rate. We did elect, on a retrospective basis, to disclose the payment of cash to a taxing authority for which we withheld shares for this purpose as a financing activity. Lastly, during the first nine months of 2017, we recognized $23.1 million of excess tax benefits as an income tax benefit in our consolidated statements of comprehensive income; this provision was adopted on a prospective basis.

New Accounting Standards

Issued

In March 2017, the Financial Accounting Standards Boards (FASB) issued an accounting standards update (ASU) related to premium amortization on purchased callable debt securities. The intent of the standard is to shorten the amortization period for certain purchased callable debt securities held at a premium. Under the ASU, the premium is required to be amortized to the earliest call date. The ASU more closely aligns interest income recorded on bonds held at a premium with the economics of the underlying instrument. The ASU, which is required to be applied on a modified retrospective basis, is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Since we have historically used a yield-to-worst scenario for our securities that were purchased at a premium, and the first call on a premium security most often produces the lowest and most conservative yield, we do not expect this standard to have a significant impact on our financial condition, cash flows, or results of operations.

Adopted

On January 1, 2017, we adopted the ASU to simplify the accounting for employee share-based payment transactions. There were several provisions that could be adopted under this ASU. We did not elect to make any changes to our method of recording forfeitures and are continuing to withhold taxes at the minimum statutory tax rate. We did elect, on a retrospective basis, to disclose the payment of cash to a taxing authority for which we withheld shares for this purpose as a financing activity. Lastly, during the first nine months of 2017, we recognized $23.1 million of excess tax benefits as an income tax benefit in our consolidated statements of comprehensive income; this provision was adopted on a prospective basis.